Is this a UTI or am i getting pregnant?? :(?

I've been scared that i could be pregnant for over a month now. Today when I wiped there's been a little bit of very very very light pink mixed in with my urine. I've never had this before. However do you think it could be a UTI? I also have to pee, like sometimes i haven't had anything to drink in a day and i have to pee with like a full bladder, it seems to be worse at night. The region of my back just above my hips/waist is very sore, its only been like this for around 2 days. In between my ribs the muscles hurt, it also feels like i tore a muscle around my ovaries I had a really sharp pain there when i climbed stairs yesterday. Like you know if you stretch you get a really painful twinge. I had been constipated so i took something for that is that a symptom of pregnancy?. But at the same time im scared i could be pregnant. Last time we had was like 5 days ago. We always use a condom...but now i just am so scared. I took plan b in december, and got a full period in the beggining of january. I also am having headaches/ neck stiffness. I went for a blood test yesterday because i am so sick of being scared but if im getting implantation bleeding then...it wouldn't have picked it up would it have. My period isn't due till like the 14th. Help im really scared. what should i do?