TTC after miscarriage

I had a miscarriage about 3 months ago. My doctor said to wait a few months to a year to start trying again. I waited till after the first period to start trying again.

But did I try too soon? Should I have waited a few more months?

I’m just surprised because with our first son, the first time we tried, we got pregnant. But now, it seems a bit harder to get pregnant. And after this miscarriage, my periods have been weird. Before the first few days it would be bright red then get gradually darker, but now it’s just is a darker red, and it lasts longer.

I don’t know, I just wanna know if this is common. Any advice?