Unprotected intercourse, he is not sure did he finished in me

Me and my boyfriend had unprotected sex about 2 weeks before my period began in March and we are both 100% sure he didn't ejaculate in me. I get irregular periods, with a few days before of maybe even a week between, but I've waited a week for mine to begin and still nothing. No pains, nothing. Last month I had my period but it was alot shorter, it normally lasts 5-6 days and is quite heavy, but last time it only lasted 3-4 and was light. About a week after my period had stopped I had a random bleed for about 2 days, and it was quite lumpy. I didn't really think much of it, so I just carried on as normal. But this month, leading up to my next period, I've been getting bubbly stomach, and I've been passing gas frequently. Im just wondering, putting them all together, could I be pregnant? But then I go back to the fact, if I had conceived back in march (around the 9th) would I have had my period on the 25th?