Could I be pregnant right after my husband's vasectomy?

Well my husband had a vasectomy in May. It took him two weeks to get completely healed to where we can have . We were careful by pulling out then but then when he took his sample and the dr said it was negative we have done it like crazy since then. Yes he has gone inside me and now I am wondering if that was a good idea. We are very fertile and on our first child it was the first shot every we found out we were expecting. So anyone think that I could be pregnant? I'm never regular and just worring a lot now.