Possible pregnancy??

OKAY SO, I've been on the pill for about 3 years now but recently have been using it as the only protection. My boyfriend usually comes inside me and I take my pill religiously so I never had a problem with getting my period late, etc. However on Saturday night we did the dirty and he came inside me but I wasn't able to take my pill Sunday morning like I usually do but I took it late Sunday night. I'm supposed to get my period today (Monday) and haven't and it doesn't feel like it's coming either. Should I be worried about being pregnant?