Hi guys, I would really really like some advice or help please. I'm 26 years old and I've never had any problems with my periods even though I've been on and off the pill for 6 years (haven't been on the pill for 7 months).

it started off with my last period being 5 days late which was so unusual for me because I've always been very regular, then it was a heavier than usual period. After it finished a few days later I had some brown discharge which I wasn't too concerned about then 8 days after my period finished I had a heavy bleed for 3 days. I went to my gp who checked for std, pregnancy and any infection (all normal). I now have had a missed period which is now 18 days late. The part that's concerning me is the last two weeks I started having really bad abdominal pain, it started off as period cramps which I thought my period was coming, also after I went on the treadmill I got really bad cramps which was weird. I also started having pain in my abdomen & pelvis which radiates to my lower back. I've been feeling very bloated and generally have a feeling of heaviness around my abdo. I've been very tired recently, I've also been having a lot of clear discharge. I had a few times pain in my left pelvis area which went down to my leg. I've been peeing more often too, I would go toilet every 20 mins sometimes after one bottle of water 

I wasn't concerned about any of this until I started having all these weird symptoms. Today I had an ultrasound which was supposed to be a vaginal ultrasound but for some reason the sonographer decided not do it because he said he can see my ovaries through the pelvic ultrasound, he said I have a 3cm cyst on my ovary but apparently they don't class it as a cyst unless it's more than 4cms. I left and felt very upset because this pain is really starting to affect my day to day life. 
I know my symptoms are similar to ovarian cancer so I'm starting to get really worried. Can anyone advise me what I can do next or if they've had similar experiences please thank you