Does Heavy And Short Menstrual Bleeding Indicate Pregnancy?

hi,

I am breastfeeding my 9 months old baby, my period was 2 days late and then started but was heavier and shorter than normal and I have been experiencing all pregnancy symptoms I had in the first pregnancy. I took a home test on the first day of my period and was negative. I also think I may have urine/kidney infection which I have quite often especially when pregnant. My question is can I be pregnant because I started antibiotics for the infection and I am worried about this