Could I be pregnant with #2??

Question....for the last four and a half months I have been breastfeeding my daughter. I work 12 hour shifts and always pumped while at work and had no problems with supply. Almost a month ago, my daughter went on strike and has refused to nurse ever since. So I started excusively pumping and for the first 2 weeks or so, once again had no trouble with supply. But the last two weeks, no matter what I do or how frequently I pump, I get less and less milk. Yesterday morning I only got 2oz when I used to get 10+ oz my first pump of the morning. Also I've had a regular (albeit more frequent than before) period since DD was 8 weeks old and now nothing. I say all that to ask this...anyone have any experience with this? Does it sound like I could possibly be pregnant again? I took a test and it was negative, but I feel just like I did when I was very early preggo with my daughter last year. I just don't have any other explanation as to why my milk dried up so quickly & no period in 48 days! We are not actively TTC but not preventing. Thanks in advance!