Periods weird after baby #5

[dizzy65]

Hey! So my daughter is almost 4 months old and I've had 2 periods, my first one was light only last 3 days with no cramping. Then 18 days later I got another one with heavy bleeding and cramps, I'm thinking this is a true period. But what was the first one? Or will my periods from now on be 18 days apart?? Yikes! Lol I'm not on birth control and haven't gotten my Tubal yet! What the heck gives? Thanks for any advice!