pregnancy sign?

I feel like it's too early but usually my boyfriend just pulls out when we have sex. I've been on birth control and about a week ago he came inside me. I don't know if it's just paranoia and my body getting used to the pill(I just finished my first cycle) or if I might be pregnant. The only off thing I feel is like something is going on in my stomach. I've also been constipated and gassy. I read it could be a sign but again I feel like it's too early? HELP