Irregular period, late and light? still virgin

My last boyfriend was extremely sexual, and had already had sex once. He was keen on sexual activities, so we did everything but sex(ie, head, hand, lick out, fingering). He only came once when he was with me, and that was in a condom (I refused to give him head without one) Theres a slight chance he could have touched a bit of cum when taking it off, because he then fingered me after that. He broke up with me the day I had my period, and then i had another regular period after that (my periods are often heavy for the first half of my period, and gradually slows down). This month however, I was a week late. One day I got brown spotting with discharge, and then the next day i had light blood come out (very little amount) all throughout the day. 10 days after that, my period came. However its mostly brown in colour, and i have light bleeding. I have small cramps, and last night i had a rather pinkish red blood thing happening. I'm curious as to why this is happening. I've had my period since i was 11, and I am now 15, 164cm in height, and 75kg. I'd consider myself overweight. I also don't consume oranges enough so I've considered lack of vitamin c as the problem. I haven't been under any major stress, only a bit where my mum has asked me whats going on with my body, and I'm stressing about pregnancy, but not in a great deal. I've also read that it could be my hormones; since my last boyfriend, I haven't been as sexually active with myself (ie, masturbation), and I'm curious if that could be a factor, as the chances of pregnancy are a million to one as I'm still a virgin. I am not on the pill either, and I don't take any medication. I was recently sick with a lot of phlegm in my body, but it only lasted a week. Could you tell me what could possibly going on with my body?