having hard time

Holly

My af is not on point. July 21st was first day and lasted the usual 4 days. My August af started 6 days late. I usually have clots but I haven't seen one little clot at all. am I going crazy or something? My son is 7 and when I was pregnant with him I bleed the first 4 months, yes I took test all were negative. I was around 18 weeks when blood test said I was pregnant... My question is can a woman's cycle all of a sudden change ie days symptoms