I'm afraid you cant return to the days of 100% trust in your wife.
I'm sorry, I dont mean to be mean, just honest.
Her affair has changed you, changed you fundementally as a person.
1.5 years is really not a long time after no contact was broken to feel safe and secure again. At least it wouldnt for me.
I dont think its wrong of you to check once in a while. it is what it is now. It is a very natural instinct for someone like has who has experienced such a trauma at the hands of those who promised to love and protect us.
Please, you are not a creepy sneak.
If your wife is 100% committed to your r, your trust will slowly grow more.
You cant rush it, I'm afraid.
Dont beat yourself up, you would truly be remiss if you didnt check up once in a while.