I think my boyfriend cheated and he wont admit it. what should i do? (i have evidence)?

Dustin and I have been dating for 2 years. I think he cheated on me 8 months ago and when i brought it up to him with evidence back then he became defensive and yelled at me and told me my instincts are full of **** and made me feel crazy. he eventually wore me out and i just gave up but it was brought back up again 8 months later when my friend was talking to a guy who had a gf and telling me everything about it and this re-invoked my feeling about Dustin. I think also because it was unresolved it keeps coming back up.

here is 10 reasons i think my boyfriend cheated on me. I just wanted to ask people who didn't know us so i can get an objective prospective on if you think im right or not and what i should do?

1. Gut Feeling

usually the first gut feeling of women are right. I'm pretty sure I can tell after to years if my boyfriend is bullshiting me or not.

2. Online

I found online she explains everything

I asked her online and she says they made out.

I ran into her and she asked if i was looking for Dustin? yet Dustin says he does not know her.

3. His change in behavior

right around that time telling me" im too controlling" and stressed him out it was his "senior year and needed time to study" and pretty much acted like a jerk to me. By the way online the same words came out of this girls mouth "too conrolling" "stresses him out he needs time to study" which is a coincidence

4. Taking time away

told me he was stressed out and he would spend more time with his friends.

I found emails asking him "Why are you pushing me away?"

5. Texting dirty to other girls

Around that time he was talking dirty to other girls, That's a fact. I found the texts. Also He would text all the time when we were on the phone and while we were together.

6. He admitted it

He admitted kissing her at the flag pole during lunch for no witnesses . i told him i needed a break then he came the next day and said he just said that to appease me.

7. Watching cheating videos

Around that time he told me he was watching videos about cheating and emotional cheating and even posted a status saying he was watching a movie about cheating.

8. He got defensive

the first time i brought it up saying im crazy and my instincts are full of **** yelling and cussing

9. Slipped up

He slipped up about sandra being her friend. "Shes friends with sandra why don't you go ask her" How would he know that?

10. When I first met him, he never had a relationship past 2 weeks and had commitment issues.

I know he loves me when i took a break with him we saw a couch about it and the couch said dustin was broken down and teary eyed when he came here. I think he doesn't want to tell me because he is afraid of loosing me. Dustin was so stubborn and would deny it the whole time. The couch gave me a lot of insight and was really good. He is a professional but im not sure if he ever did relationship advice before. the couch made it so that even though he did or did not do it he learned from it. But i dont like that at the end he asked Dustin like 10 times if he had anything to do with this girl at all and Dusting kept doing wrong body language until like the tenth time the couch said "oh he is telling the truth" and he asked me if i believe that. I said no, and the couch just told me it's because it was stuck in my head already and that we'll work through it together.

Now it really made me feel crazy I can't believe that. I'll always know the truth no matter how many times he denys it, i told him that. It's so hard to trust him now. I think the least I deserve after what happened is for him to admit it and an apology and I would forgive because I know he learned from it. I just feel it's still unresolved and have some hatred to him for it. I told him if he ever even THINKS about cheating again to break up with me. I am really insecure now and always checking his phone.

Should I just drop it and let it go? What should I do? How do I stop feeling insecure around him and trust him again? (sorry it was long..whew)