Bunny, I've faced dark nights and wondering whether I'm flawed, bad, narcissistic, and god knows what else.
Truly, I believe that because you are concerned with your own morality, that you aren't a bad person. On the contrary.
I have also had suicidal thoughts, many times, never with the intent to act on them.
Many people have them.
Alcoholic thinking? Maybe. Or human thinking.
I have survivor's guilt, regular guilt, and complicated grief over my mom's suicide and the events surrounding it. Lots of guilt, sadness, anger, and so on.
What you feel about your sister-in-law being pregnant is quite understandable, in my opinion. Don't feel too bad feeling this way. I really mean that. It will pass.
That said, have you considered trying to conceive without a partner?