Help. No idea.

So about 5 months ago I had sex - started feeling off that day of having sex. Still feel abdominal feeling till now, but I got my period every month. so I can't be pregnant. But I have my boyfriend who ended up finishing in me the next the day he bought me the morning after pill. 3-4 weeks later I got a pregnancy test and it came back positive, well the second line is faint but definitely there. If I was pregnant it would be with the second guy right?