When to be Worried About Ovarian Cysts?

I had a ovarian cyst with fluid buildup up which caused an infection cyst wasnt bad they were mainly worried about the infection I had some symptoms that I thought were important my doctor told me to go in everything was fine and my levels were clearing up this was a few days after antibiotics I also have an ultrasound on the 13th and a few days ago I had my iud removed I only had it for a few months and I didn't have a period when I had it but I got it taken out and ever since then I've had terrible cramps and lots of waiting and I maybe it's a. But I'm a already keeps telling me that it's something serious someone help me understand when to be worried about it being serious