3.5mnths PP, 2nd period, pain, breast changes, spotting...??

So, my twins are 3.5 months old. I had a csection. i bled for about 2 months afterwards, during which, my obgyn said i had my first period postpartum. So, a month and a half later, my boobs swell up, and i have mild- but periodlike cramps on both sides. So, i'm thinking, "ok my period's coming". That went on for about a week and a half, and then BOOM- i bleed like crazy for 4 days. My period. I've stopped bleeding now for 3 days, but my boobs are still swollen and tender and getting more tender as the days go by, and i have mild occasional cramping on both sides.
My husband and I are not using protection. Our choice. We know the risks. My dr keeps telling me it's normal, but he ignores a lot of issues...

Any ideas what it could be?