Prolonged bleeding and possibly pregnant

I have been on my period for 17 days. Period came when expected and started out normal but by day 7 was not stopping.

Seemed to slow down in the second week but by day 14 was back to being dark red rather than brown blood and was slightly heavier again.

It kind of felt by day 14 like my period was starting from day 1 again - I had some mild cramps/fatigue and still do now on day 17. It's not heavy enough for a tampon and 1 pad is enough for the day. Seems to gush out when I use the toilet but less so when I'm moving around. Had some small clots in the first week but none now.

Up to this point my cycles have been around 25 days long and are very predictable.

I explained situation to my GP who prescribed Provera to stop the bleeding but advised before taking it that I take a pregnancy test. I did one this morning and it has a very obvious positive line.

Now I am scared. I go for a scan tomorrow (nurse said I could be 6 weeks pregnant going from the date of my period before this one?) but it seems like the doctors don't really know what's happening. I haven't missed a period. Am I having a miscarriage? Could I be pregnant and everything be okay?

We have been trying for a baby for 18 months now so to lose a pregnancy now would just be the biggest slap in the face

Any advice or words of comfort appreciated, I am so anxious right now and I'm shaking