Am I pregnant?

So my boyfriend and I had sex twice 5 days after my period ended. He finished inside once and pulled out the other time. My current period was due this past Saturday and til today I have not had my normal period. It's been brown blood and it is only when I wipe, I really don't even need a pad. Sometimes there is some blood ie. red spots but the majority of the blood is brown. For this reason I have taken a few pregnancy tests, all negative. I am extremely tired at times, nauseas, irritable and I think I missed my current period. It's all very frustrating not to know what's going on. Any thoughts? Thanks!