Morning after pill or not??

So long story short, I haven't been super consistent with my birth control, I miss at least 1 day a week. My boyfriend & I had sex on Friday night and he came in me (he usually pulls out because we don't use condoms and were paranoid lol) I got my period over Valentine's Day, was off for a couple days and then oddly got it again this past Saturday.  So my question is ... Should I take the plan B pill? We don't want a baby right now but the pill is expensive & I don't want I go through the process with the pill if I don't necessarily need it. Any opinions?