Hi MG,
I went longer than you before starting AF. After my first, I had only a couple of cycles before conceiving again. They weren't heavier, but they were longer (more days of bleeding). Then after no 2, they were heavier, and clotty as you describe.

It seems that many women have a different AF following pg. There is no guarantee what it will be like. My doctor told me that hormone falloff in the second half of your cycle can be irregular, esp in the first few cycles following a pg, but things should settle into a pattern after that. If they continue to be very heavy, check with your doctor.

You should be able to use tampons. I ended up having to buy the super-duper tampons after having always used the "normal" absorbency!

I just had my first AF following DD's birth, and it's very light, as they were after DS no 3. So if you decide to go for no 2, things may be different again. HTH!