My car seems to be getting sicker..:(

I own a 92 Stealth TT, that has 78k miles on it and 4k on engine, that was rebuilt by previus owner after a spun bearing. Well after i bought the car a turbo blew so i spent over 1k to fix that. it ran good for a while then i started to notice the low oil presure light would come on after driving for a bit while idleing. I had the oil changed with some additives to raise the pressure. Good Year found out that the head gasket was leaking and caused a slow oil leak...(they wanted 1300 to fix it so i decided to wait a bit) any ways the oil pressure problem seemed to go away for a week or so. Now its back and worse than ever. Anything from having the lights on, A/C, radio, ect seems to make it worse. When i turn them all off the oil pressure light is dim and comes on off and on when ideling instead of being a constant bright light when all that stuff is on. And the finall prob is that my idel has been very irratic the last two days, going from 600RPM to 1k,m would that be the IAC?
Thank you for any help possible, sorry if its hard to understand, in a hurry.
Thanks again,
Gavin