Strange period - help!

Hi guys, the last time I had sex was the 20th may. Since then I've had headaches, nausea, constipation, stomach pain etc. Around a week ago I got some bleeding but didn't seem to be menstrual - it was dark brown almost black in colour, very heavy consistency and wasn't enough that I had to wear a sanitary towel (just wiped myself every few hours) 8 days in it has now turned the normal bright red colour I should expect although I don't have that usual 'feeling' you get whilst menstruating. I'm not sure if this should be something I worry about although me and my boyfriend are anxious, I'll be going to get a few tests soon just to be sure.