Pregnancy #2

So I am 24 weeks pregnant with my 2nd little girl and thank God she is healthy, but this has been an awful experience for me.  At about 16 weeks I started having headaches and dizzy spells every time I stood.  After a couple weeks and several different Drs I was diagnosed with pots.  I have been out of work already for about six weeks and they just put me out for the remainder of my pregnancy because I am too symptomatic and by that I mean that my heart rate goes from about 65 when sitting to about 120 when standing along with a bp drop.  Disability has yet to kick in so right now my husband and I are trying to use my inheritance from my dad to support my half of the bills.  Add to this I am not healthy enough to go to work, but i am still trying to plan all my lessons and grade all my papers because I'm a teacher.  Pots with a two year old(almost) is not only challenging but heart breaking.  In order to take care of myself to take care of my unborn child I feel like I am neglecting my daughter.  I cannot stand and hold her, my husband is the one who sings her to sleep every night because rocking in the rocking chair is too much for me most nights.  I have to get any other family member to take my daughter to mommy and me dance because she loves it but I can hardly stand.  I am cooped up in the house all the time and I feel like my family is suffering with me.  Now I am starting to be terrified of the fact that once my second daughter is born atleast at first I may not be able to care for either one of them.  How do you deal with that as a mother?