Help...lost and confused!!

So Google doesn't help at all... And every time I look at a news feed or some type of blog I could never get to the real answer. So I have super irregular periods I think before this past one I hadn't had a period from the end of February until the end of April. So after the worry of that on my shoulders I finally got into a relationship and finally had sex. Well we had sex on June 11th around 11 pm to 12 am, well I guess I could say when o woke up my period had came down. It was light which was abnormal as ever. When my periods come down they are heavy and I have horribly cramps. My period was light and very pink than red. So now it's a month pas and my period has not came yet. Two weeks ago I had a UTI. (Never had one of my life) and I feel like I might have another one coming on. My symptoms are I'm fatigued (but I feel like I'm always tired so I don't know if that could qualify as a symptom). I only have mood swings against my S.O. My lower back hurts on the constant side. ( mostly when I sit for too long or lay a strange way). My nipples doesn't hurt; they usually do when my period is approaching, but nothing and now im 6 weeks past my period which is well over a month. I took a test it said negative but I feel like it may be wrong because of my symptoms. Can you guys tell me what you think?!