Jinnifah

I'm 20, and my period is usually regular - every 18 days. I started having sex a couple months ago and since then (sor some unknown reason) the length of my cycle increased by 4 days. This month my period is another 2 days late and i noticed this morning that there was some blood when i went to the bathroom. I thought my period had started, but that small amount was all i've seen all day. Could i be pregnant? I have also had very tender breats, and severe cramping the last 2 days. I wouldn't be so confused...except my boyfriend and I always use condoms and we've never had a condom break. We have fooled around naked and there has been precum, but no ejaculation. Any help would be greatly appreciated. thanks.