Irregular Period

So my sister and I have been having this problem for a couple of years. We never really worried about it but now I have started to worry. And I’m too embarrassed to go to the doctor and tell them that it’s it’s been happening without me worrying. Here ‘s what’s up:

My sister and I both have been having irregular periods. For me they sometimes happen once every 2-4 months and maybe last 1-3 days. When I do get mine and it lasts longer the blood comes out in clumps. I tried to research but have had no luck.