Take care of yourself...Eat right...stress is not good but you also could not be eating right or drinking enough water hence dizziness, nausea.
You need to take care of yourself so you can care for Chirp & Roxie.
Have not followed Chirp that much so not sure what he is going through but some budgies can get sick young...Poor breeding & early care or disease from crowded conditions before you get them.
You do the best you can to make there lives happy & comfortable. Nothing more you can do & certainly do not blame yourself because there is only so much you can do.
I'm like you...no social life...not really any friends but that's what I want...that's what works with me as people & interacting with them is stressful!!!! Please try to do things you like to do. Watch some movies...draw etc...
Stop worrying that's theres something wrong with you or you can do more...Your OK the way you are & just embrace your uniqueness...
Find things in life that bring you joy & embrace them...Work on that...breathe a bit...take it one breath at a time & try not to think too far ahead of yourself..