late period, fatigue but it's my second cycle after stopping breastfeeding...chance of pregnancy?

I am 5 days late on what should be my second period after my baby. She's 7 months. I breastfed until she was 5 months and I got my period when she was 6 months so now I should be on my second period and nothing. I took two tests but later in the day ( I know they say first urine is best) I've been feeling really tired and like I never get enough sleep. This was also my first symptom when I was pregnant with her. And today I also experienced car sickness which was also a symptom with her. With my first I didn't test till I was 6 wks pregnant. And showed up right away. Could I be testing too soon? Should I test again? Anyone had a similar experience ?