I haven't been on my period for the last 4 months and I think it might have been my implant, I have had it out within the last month and still didn't have a period. Since then I have had unprotected sex and had signs of pregnancy such as tender nipples, abdominal pains, going to the toilet more often and lower back pains. It has been around 2 weeks of unprotected sex and now I've come across really heavy, bright red vaginal bleeding with clots of blood. Could this be a miscarrige?

Eh, id say no. If its only been two weeks since the unprotected sex, tge embryo isn't developed enough to cause a ton of tissue loss, id guess if you miscarried at 2w gestation, you wouldn't even be able to see it I don't even think the egg is implanted to the uterus by that point, but I coukd be wrong about that. If you haven't had a period in 4 months, your period is probably just heavier than normal, that would happen to me when I was on the pill and would skip my period for three months. The signs you had could be pms or your body creating pregnancy symptoms depending on how much you've stressed over this, but overall id say you didn't miscary. I miscarried at 2 months and experienced more of what you're talking about, but with my son I didn't have any signs I was even pregnant until I was 6 weeks.