I’m going to get tested...so embarrassing being a married, monogamous woman :(
I was also thoroughly embarrassed that I needed to get tested, but it is truly not your fault. It's likely that you don't have anything and have nothing to worry about, but better safe than sorry. If you can, have someone you trust go with you to get tested. I cried the entire time I was in the doctor's office, and having my mom there was a huge help. Unfortunately, most health care providers have seen this thing before, but the good side to that is that they know you are in pain and they also know not to shame you. My doctor was incredibly helpful, and once she knew I was there to be tested due to my husband's infidelity, without me even having to bring it up she asked if I had been having trouble sleeping (as so many of us BS do) and when I said yes, she prescribed me some Xanax, no questions asked! Also, as painful as this is, you will need to go in and get tested a few more times in the coming months, as some STDs can take longer to show up on tests than others.
His story keeps changing. I am slowly cutting off the “snake”, but he basically told me he still has blinders on for this woman and is trying to paint me as the “obsessed wife who won’t let go” because I came back to the house and only got something minimal.
Oh boy, the rewriting. It seems that your husband and mine would be best friends given how similar their behavior was. According to him he had been telling me he was unhappy "for 6 months" and his favorite line whenever I asked how we got here is that "You just don't listen to me" even though he had recently bought me a Best Wife Ever t-shirt and we had been trying to have a baby for the last 4 months leading up to the discovery of the affair. On the day I caught them in bed together, he screamed at me telling me that I am looney, and "I'm really starting to get concerned that something is mentally wrong with you, because you just aren't getting it!" I know it is difficult, but do not let his rewriting make you question yourself! You will find yourself with a lot of time on your hands, and you will likely start to question if you could have done anything differently, or if any of your behavior pushed him to do this. The answer is absolutely not! His actions, his choices, not yours.
I too left the house. The lease was in both of our names, but knowing that if I forced him to leave he would also force my step daughters to go with him, possibly to the OW's house, and knowing that I could not legally make him leave them with me, I decided it would be safer for them for me to leave the house. As someone else mentioned, it is likely that the house is marital property and that he cannot prevent you from going there, though he will do everything he can to make it miserable for you. Mine installed a deadbolt and a chain (both illegal to install in apartments due to safety concerns) and I had to get my landlord involved to get back in and get my things. I would not be surprised if your husband changes the locks. I would consult with a lawyer to see what you can do if that situation does arise - you may have to get the police involved to get back in and get your things. If your plan is to stay out of the house, then get a Uhaul and get your stuff our ASAP. Even if you have to rent a storage unit for now, it is better than having your stuff sitting in the house, and him able to do what he wants with it. Trust me, my husband had already started throwing things out by the time I came back 5 days later.
Also, he does not seem like a safe person to be around, so if getting yourself out of there is the healthier choice, then screw the "he should be the one to leave, he cheated" mentality and just get yourself into a better situation no matter what! An attorney can help you figure out your rights in regards to the house, and honestly, if he is forcing you out by taking your name off of everything etc., that might give you leverage in your divorce. I know that is not something you want - trust me, I would trade anything to be married and happy again - but like Falc said, unfortunately the person you thought you knew was just a facade.
Also, I agree with a few members here that this complete 180 might signal some sort of substance abuse. After Dday, I ended up finding paraphernalia and substances around the house, had them tested, and found out he has been using meth. Because the paraphernalia were common household items (pens), I had never paid any attention to it before, but I figured out that it's been going on for years. Substance use may or may not be the case with your husband, so I don't want to project, but just something to think about.
Also, my husband's strange behavior (going out on his own more, talking about all of the "pressure" he was feeling etc.) started pretty much immediately after we started trying to have a baby, and I discovered the affair approximately 4 months later, so the timing there is similar to that of your husband's (you mentioned that you two were supposed to start trying next month, I'm assuming that means you've been talking about it for a while). There is something to be said for the pressure that a narcissist starts feeling when they realize that their life might not be completely centered around themselves anymore.
As many have mentioned, you are so much better off! I know it is hard to hear. As a woman who was also trying to have a baby, I understand the pain of realizing that your dream of having a child is going to be put off for a while. That in itself is its own loss that you have to grieve, in addition to the loss of your marriage, and the person you thought you knew. But please know that you are absolutely 100% better off not having children with a man who could do this to you!
Don't forget to take care of yourself! Losing weight in a time like this is normal. Protein shakes were the only thing I could stomach. See your IC regularly. Also, it will help to document everything in a journal. Wishing you the two things I know feel impossible to get during this time- some peace of mind and some sleep!