Cycle changes after miscarriage...?

I was 11 weeks along when I had a miscarriage in May. My next 2 periods were very heavy. It has settled back down but now my cycle length is shorter by 5ish days. I've also had spotting for a few days both before and after my last few periods. I have 3 children and my cycle changed a bit after each pregnancy but these recent changes are drastic. I called my OBGYN and they said they could do a special type of ultrasound but I'd rather not do that because I don't really feel like there is anything "wrong." It's just different. We are TTC again so I'm extra aware of these changes. Has anyone else experienced something similar?