My period was a bit off in the last one year: 22-35 days of the bleeding start and 10-12days in length

Hello, my period was a bit off in the last one year: 22-35 days of the bleeding start and 10-12days in length. The amount was normal. I went to see the doctor a year ago and after a blood test which result was normal, she said she can only give contraceptive pills which will regulate my period. I’m 28 and trying to get pregnant so it wasn’t an option for me. 10 days ago (18th day of my period and no bleeding before) I felt a sudden warm flow and two handful of bloodclot just passed through me. It was around 7am and since then I had to change the menstrual cup in every 40min as it overflow. Each time it was filled with blood clots , many of them 20cm long. I called my GP at 2pm, been the practise at 5pm, as I felt really weak. The nurse gave me Tranexamic acid tablets which I didn’t take as after arriving home at 6:30 it seems to be less bleeding on its own. I had a blood test on the next day when I didn’t bleed at all. And the gynaecologist from the GP called me on Friday. She sad again that the blood test is negative so she can’t do anything with me if I don’t want the pill. I told her that I would like to find out what causes it but she refused. I had to lie that many female family memebert had polyps and I’m worried it’s running in my family. This was the only way to get referral to scan. She said if it comes back negative she won’t deal with me, take the pill or nothing. I didn’t have the scan yet bu my period started yesterday with the same heavy bleeding exept no bloodclots. I’m bleeding now as weel and today I see many blood clots and my menstrual cup get totally full in 30min. I took the tablet from last time hoping I can do some of my task today but I have practical in 2 hours and I can’t even make it to the uni clean. I really don’t know what to do if the scan won’t find anything.please give me advice