Jen.....lovely to see you on here but you have my sympathies. Your low levels of sleep will magnify everything I suspect.
Indira (lovely name) is still very young but maybe try a routine with her? I recommend Gina Ford's. The book is hideously prescriptive but IT WORKS! It took away all my not-knowing-what-to-try-or-do-next-ness. I wonder now if I had mild PND as I cried so much at the beginning and really felt I wasn't coping well. I think it's pretty normal but doesn't help when you don't know what to do to help your baby. I tried the routine at ca. 8weeks and on the first day, I was on the phone at the supposed miracle 2hours up/2hours down trigger time and lo and behold, Maya fell asleep in her Moses basket, on her own, bang on schedule. After that it got much easier. Before we started the routine, she often used to sleep on me in the wee hours as it was the only way (DF at work). I had to sit upright and so your comment about 2-4hrs sleep is v.familiar. Can you ask someone kind to come over for a couple of hours one afternoon or evening whilst you nap or even just take a long bath? it sounds crazy but it really, really helps. Don't do housework before they arrive, just tell them it's not a visit, you need a break. You need all your energy and wits to cope with the new arrival and not sleeping makes everything so much harder.
Have you tried taking her for a stroll in the pram? go on a circular trip until she falls asleep, then head back asap. Leave the pram in the garden with an insect net and take a nap yourself.
I've also read that taking them to a (now this is where I'm crap), either an osteopath or a chiropractor is very helpful. I can't remember which it is. Hopefully someone less crap than me will remember...
This period of sleeplessness does pass, I promise.