1st AF after miscarriage

Nicola • Married. 29 years old. Mmc at 11 weeks July 2015 and mc at 4+3 weeks Nov 2015. Pregnant with baby girl due 30.07.17 ♡♡
I had a miscarriage 5 weeks ago and got my first AF on Wednesday. Today when I got to the toilet it's hurting :'( whenever I push/strain it starts to hurt and I'm having bad cramps. Is this normal for my first AF after miscarriage? The bleeding was heavy yesterday but is lighter today.