1. I don't think it's relevent whether you were gay or not, I think we should care more about how good of a person we are, that's what would define your value and that's what we should feel shame about, it's when we treat others poorly that we should feel shame.
2. being a good person and treating others well include you too, you want to treat yourself well, too
3. do you think it's wrong to be gay? if you don't know, then who does?
4. It is important for us to feel accepted for who we are, before we can learn to accept ourselves. I can see how all of this can make it hard for you to challenge that negative belief. do you challenge though? do you tell yourself it's not true?
5. Work on resilience.
6. I see, it's not about trusting that things will work out if you approached these difficult conversations. it's more about trusting that you can handle it
If these thoughts recur beyond this time when you're stressed, CBT might be an idea.
In the meantime, it's important to remember that she cares about you, is happy to support you and there are options for when those close to you can't figure your problems out - they aren't pyschologists/therapists and it's ok that they don't know the answer
It doesn't belittle your connection, their love for you, or mean there's something "wrong" with you