Huge blood clot and breakthrough bleeding whilst on the combined pill. Really worried.

[Bluebird2588]

Hi guys. I was diagnosed a couple months ago with stage 4 endo and fibroids. I am having surgery in January. I've been on the combined pill (taking it continuously) for two months now and I've been told to continue with it until my surgery. I was advised to switch to zoladex but after researching I decided against it. The pill worked at first and stopped my first two periods but for the past week I started bleeding, it started off as spotting but now it has got really heavy and last night I passed a really big blood clot. It was horrible. I've emailed the specialist nurse at the endo centre that I with but she hasn't got back to me. Should I be worried ? The GP said that bleeding can happen when on the pill, and you can get blood clots. This one was so big though. What do you think I should do?

Just been so worried and scared about it especially because the pill was working for a while.