I really hope you won't be relying on the views of this thread to determine paternity based on a likelihood of which guy it is. You do need to be looking at a DNA test. Pulling out is not an effective method of contraception and I'd personally say your being abit naive in your thinking about that.
I'm not criticising or judging because I was in a similar situation years ago. I was almost certain it wasn't the 1st guy because I was almost sure he hadnt fully ejaculated or at all, plus I bled like a normal period after that last encounter. The second guy was a brief one night stand that spanned over a weekend.
I tried to match all my dates of every scan, added with the fact I had what I assumed was a period after 1st guy, and opinions from others and came to the conclusion throughout my pregnancy that it was much more likely to be the 2nd guy.
Unfortunately as luck or karma would have it, DNA testing found the 1st guy (abusive ex, who i prayed and had calculated numerous times wasnt) was infact the dad. It ruined my life for a long time.
I'm not saying your situation will turn out like mine and guessing may actually lead to the right man but my advice to you would be, if there is doubt, unless its in concrete black and white, you will never truly know for sure who is your baby's dad is based on likelihoods and possibilities. For your own sake, Take the test and in future find a better method of contraception.