Pregnancy and calories??

I just found out I'm pregnant and am almost six weeks along. I haven't been to the dr yet...but before finding out I had lost 80 pounds and had been eating around 1200-1300 calories a day while walking 4.5 miles almost everyday. I've seen that they say 0 calories added for the first trimester and then 300 second and 500 first. But is that for an overweight woman? And should I up my calories this first trimester from 12-1300? I'm still gonna keep exercising but confused about how many calories I should be eating, and when I do exercise should I eat all or some calories back (I hadn't been previously) I've also had a terrible time with my eating this past week and the scale says I've gained ten pounds...yikes! I'm assuming some of that is bloating from how poorly I've eaten though. Sorry if this doesn't belong here...just hoping someone can help me out here!! I have a 9 month old baby and with her I did not watch what I ate at all and ended up only gaining 4 pounds...but with all the hard work I have put in I wanna make sure I keep being/eating healthy and my baby is healthy too.