"Maybe" Pregnant And Alone

After a couple of terrible relationships followed by even worse breakups, I decided long ago that I was just going to give up on the whole relationship thing. My new plan seemed to work for a while until my sexual desires began taking over my life. I was always feeling the need to "get off" and my fingers/toys where just not doing it for me anymore.
So one day I was talking to one of my good guy friends about my problem and he came up with a solution. His solution was for me to basically use him for sex anytime I wanted, no strings attached. Well this obviously sounded like a great idea to me and so I followed through with it. For the first time in my love/sex life, things were going well . . until I realized that I skipped my period not once, not twice but three times! Yes, I went three whole months without my "monthly gift".
Now I'm sure a lot of ladies would love the idea of not having their period and for I while I really was kind of happy about it. Then it hit me, and I suddenly became worried. Three months ago, my friend with benefits and I had sex. During the sex the condom slipped off but he quickly replaced it with a new one after realizing what had happened. Now that was just something that we really didn't think about at the time. But now we're forced to think about it.
Just recently I told him about the situation and of course, he was in complete shock. He offered to take me to the doctor and promised me that if I really am pregnant then he would take full responsibility and be there for me. But this was just a couple of days ago. Starting since yesterday he just stopped talking to me and accused me of lying about my missed periods.
It seems that the stress is getting to him more than I thought it would. But yeah, I cant blame him. It sucks when you go from "friends with benefits" to "maybe baby daddy".