There's another post over in the general forum by iris2536, about why childless betrayed partners are advised to RUN from the relationship and file for divorce.
I think you might find that thread interesting. Hindsight is 20/20, and many betrayed spouses look back and see all the red flags that they might have ignored or missed over the year, so keep in mind that any advice to RUN now is because they want you to avoid the additional pain and difficulties they face involving houses and shared debts and children.
Having said that, I'm actually NOT going to advise you to run from the relationship, because I agree with iris2536, that it comes across as dismissive of the love you may still have for your wayward fiancé.
HOWEVER, I absolutely do believe that you need to cancel (or at least postpone indefinitely) the wedding immediately, for a few reasons.
1. You need time to process what happened. I know 2-5 years sounds like a long time, and I remember thinking I would be over my WH (wayward husband) cheating sooner than that. Well. No. I'm starting year two, and while I've healed a bunch and am better than I was, I still deal with triggers, flashbacks, insomnia, nightmares, depression, panic attacks... many BSs (betrayed spouses) deal with symptoms of or full blown PTSD (sometimes referred to as PISD --post infidelity stress disorder).
2. Right now you need to focus on taking care of yourself, NOT last minute wedding plans. That means get tested for STDs, find a therapist that has experience with trauma and/or infidelity, consider antidepressants if you're really struggling, do your best to get sleep and keep eating. It's not unusual for BSs to lose A LOT of weight quickly and end up being hospitalized for malnutrition or fainting or having some other stress related illness.
3. MAKE SURE YOU STAY HYDRATED. Not with alcohol. And if you have no appetite or trouble keeping food down, consider sipping on a protein shake throughout the day instead of water.
4. If you go ahead with business as usual and/or get married not to rock the boat/embarrass anyone/lose a deposit, then your fiancé will assume that the next time she slips and cheats you will forgive her again, OR that she can guilt you into keeping the status quo ("how can you break up our family and ruin our children's lives? I *only* blew the softball coach once! And it meant nothing!"). Actions have consequences. Don't think of what you do going forward as punishment for cheating, so much as putting your health, safety, and well being first. If your WF is TRULY remorseful for her actions, she will move heaven and earth to work on herself and make sure she becomes a safe partner who would NEVER do this to you EVER again. She will accept your hurt and anger and mistrust, because she realizes that her actions caused them to happen. Full stop. No blame shifting ("you didn't pay enough attention to me!"), no excuses ("I was drunk!"), no guilt trips ("but my parents paid for XYZ and now they'll lose that money because of you if you cancel the wedding!"). Instead, "I understand why you need to cancel the wedding. I'm sorry for what I did. I will make all the arrangements and notify all the guests. And then I will get myself into counseling to figure out why I would throw you and our relationship away for some strange dick."
Pick up a copy of How to Help Your Spouse Heal from Your Affair by Linda MacDonald. It's written for the cheating partner, but it will help you to see what true remorse is. Do NOT settle for anything less.
And lastly, please do not be ashamed or embarrassed to cancel the wedding. Your fiancé did this, not you. It's hard sometimes right after d-day (day you discover the cheating or affair) not to let your thoughts spiral into blaming yourself or thinking you could have done something different. Your self-esteem takes a beating. But there's nothing wrong with you. YOU did not cheat. SHE did. There is something wrong with her, that she needs to work on. Morals, boundaries, character flaws, FOO (family of origin) issues, whatever. And you can't control another person or what they do or do not do. The only person you can control in this situation is yourself, so please, cancel the wedding and step back and give yourself some time to make any decisions.
It might not feel like it right now, but you WILL be okay. You're young, if you want to have children, your biological clock isn't ticking, and you have time to figure out your next steps.
Post as often as you need to. We're here for you.