Confused about net calories/deficits.... HELP!!

StandStrong32

And Please, Don't try to make me feel like an idiot. I am honestly confused and can't seem to find anything that helps my confusion.. actually makes it worse!!

I am trying to lose weight and have been using MFP since June 25, 2012... with 1620 being my goal for calories to meet my 1st goal weight. We are now at July 26, 2012 and I have lost 4 pounds. Now, I know that sounds like a lot but I lost 3 pounds that first week and didn't loose the fourth pound until this week that we are in... I also have Hashimoto's disease (which means I have an underactive Thyroid which means low metabolism) which is supposedly in check now with medication and two days ago, I started taking 2000 mcg's of B-12.... so how else can I try and bump up my metabolism??

I have an office job so am sitting most of the day. I am upstairs so therefore I ALWAYS take the stairs and most of the time I jog them up and down. I also have a walking buddy and we are walking 3 miles plus a couple of cool down laps for a total of 60 minutes every evening....

How do I need to calculate what I need to eat (calories) in order to lose weight... preferably 1 lb a week??

Thanks in advance for any help!!