Overweight

Ok so I have lots of health problems and I haven't been able to keep up with my health the past couple years. After I had my first I got very depressed over the fact that I couldn't produce enough breastmilk for my baby. I lost all care for myself and quit working out/eating right/just being smart. I can't work out much anyway cuz I have asthma as well as a really bad knee. I am under 5'4" and got up to 184 lbs after my first baby. Now pregnant with #2 and I lost down to 170, but no where near where I should be. I am panicking over gaining weight because I am not happy with where I am now. I tried keeping active but was spotting a lot and having bad cramps. I've been taking it easy but I am so scared of making myself bedfast by the end of this pregnancy because of my weight! I can't eat what I need to because I have been throwing it back up. I can only eat like soup and crackers sort of thing. 
I just need a few words of encouragement so that way I don't lose my cool completely and stress myself out!
UPDATE: I live in the middle of nowhere near the Oklahoma panhandle. I don't even know where the nearest pool is. But I'll keep my eye out. I haven't been able to afford a gym membership or an exercise bike lately but I'll keep my eyes open for one. Thanks for the tip!