just need some help

i have a number of questions i just dont know the answer to. if anyone replies it would be greatly appreciated.

Okay, i have reached the weight i first set out to achieve; I'm am just slightly over 7st. My friends and family see a change and say I've become slim however although i do see a difference (my start weight was around 8st albs) i don't feel that slim nor do i feel as slim as i thought i would when i did achieve it. Is this normal? I know i wasn't fat at the start but i started a 'healthy' lifestyle and the weightloss has come as a result of that.
My goal calorie intake suggested by MFP was been around 1,500 but truthfully rarely come close to eating that much daily. I have been eating anything from 700-1000 calories a day plus exercising twice a week at the gym as well as little cardio seasons everyday (excluding saturdays) since just before april time.
I take it my 'healthy' lifestyle wasn't as healthy as i thought as i haven't had a proper period since around april. I take it this is due to my lack of calories daily? I am too afraid to eat anything more that what i had been because i didn't want to ruin the progress i'd already made. I am so much more confident in myself now so how do i go about maintaining my weight instead to losing weight? do i exercise less, eat more or do i have to keep everything the same to maintain it? if i up my calorie intake will this cause weight gain? i am so much more confident in myself now. I want to stay this way. how?
Also if i go from losing to maintaining will my period come back. will my period come back ever? how?
any replies will be great thank you