I Had Sex On The 12 Th & 19th Of

I had sex on the 12 th & 19th of March . My period started on the 7th of March & Feb 8th. My cycle is about 27 days. I was supposed to get it like on 2nd of April. My period was about a a week late, which isn't normal. My friend and me are just a day apart on our periods. Hers is ending now and mine just started but it doesn't seem like my period. It's really really light. It started out pink and then this morning it was brown. Right now it's red but still really light then normal. I've been really tired lately, cramps but not that severe. Moody & constant headaches. Nauseous throughout the day. My back is still hurting. My nipples were a little sore the past couples days. I'm been forgetting a lot of stuff especially today. I did take a test a over a week ago and it was negative. I did have sex on my fertile days & after my last period ended. I don't know if I should wait a couple more days to take another test. Or just not to be worried. My period is just never this late and never this light.