4 weeks pp

I'm 4 weeks pp and some days I feel like I just did a million sit ups, like a deep pain, not cramping. I didn't have this with my first son so I don't know if this is normal? I realize I just had a baby and carried him for 9 months but I just felt really good after the first ds. This time I feel so crappy most of the time still. Anyone else still feel this way? Oh and I'll go like 3 days without bleeding and then bam I'll bleed some, luckily I am still using panty liners.