I'm 17 soon to be 18
I'm on no protection and also have unprotected sex

I had sex on the 25 of March and was meant to be on my period on the 3rd of April.. I was 2 days late & had bloating, bad gas, pains in the bottom of my stomach, tiredness and moody, I did 2 tests but they came up negative I did them before my period I did one on the 30th of March & one on the 3rd of April.

Today I had serious pains and had light pink bleeding.. Then hour later had normal red... I put a tenpac in and then hours later it was red blood, see through stuff and also brown stuff? I'm so confused and need help! I'm still having pains on the left side but keep going & coming back? But I've never had cramps or anything when I'm on?
Today I had brown and red blood? Is that bad or what I'm so confused someone help me