honestly, the best thing you can do right now is to get an accurate bodyfat reading. that's going to be the best gauge of where you can be. in the meantime, your bmr and daily activities without exercise are 1810 cals. which means that even if you weren't exercising, you already have a 500 cal a day deficit. that's just too much. if it turns out your have 40% bodyfat, then by all means, you can probably lose a pound a week. but if you're more like in the 20s already, then you just don't have enough fat on you to lose a pound a week. you want to be aiming for no more than about 250 cals. so you need to figure out how many more calories you are burning through exercise, and you need to be eating them all back to maintain that 250 cal a day deficit. and you don't have to eat it all everyday, just that on average you are eating about 250 cals less than you burn. so even without accounting for any exercise, you're eating about 160 cals too few.
do keep in mind that what was possible for you high school [the leaner 150lb weight] may not be possible for you since you have aged. it's entirely normal for women to put on a last bit of growth and fat at the end of high school and into college. you might be able to get that shape back, but you may also need to weigh more to do it [ie carry more muscle around]. it's just that as we age we tend to settle a little differently, which isn't a bad thing, it just means that we can't expect to do everything the same way we did when we were younger. you may also find that you're happy a few pounds lighter and a little less lean. it's all going to depend. but the really important thing is to start eating close to where you should be maintaining, otherwise you're just going to be stressing your body out. if you've been eating this far under where you should be for any amount of time, you might have to spend a few months in a regain phase while your body adjusts to where it should be.
it should be pretty easy to boost your portions: have 1/3 cup instead of 1/4 cup oatmeal, add a few more strawberries and blueberries, use 1/3 cup greek yogurt instead if 1/4, 1/3 cup beef instead of 1/4 cup, 5 teaspoons or 3 Tablespoons of beans instead of 2 Tablespoons, 30 almonds instead of 24, 3oz chicken instead of 2oz.
-google first. ask questions later.