I'm starting to uphold my boundaries and keep my distance from toxic people, but I can't shake the feeling that I'm being a bad and selfish friend...

Two recent instances have happened...

One is that a former friend who has been very troublesome in the past has contacted me again after many years, has a lot of drama going on (including legal), and I just have a very bad feeling about the entire situation. None of what they have been telling me is adding up (not that it's any of my business, but they are accusing some people of some very horrible things, and with the way they have a history of saying untrue things and their stories are fishy now, I'm afraid they will make something up about me as well), and I just have a horrible gut feeling about being involved with them again. I’ve talked to some trusted people about it, who have told me to stop answering calls, so I have. They still call and I feel terrible about it, but I also feel that I need to protect myself and that the feeling is there for a reason.

The second one is that someone wants to stay with me for an extended period of time to take part in something they don't want others knowing about, and I'm also very uncomfortable with that and have told them no. Their reaction is... not good. They're pretty upset with me and I already feel guilty.

Both of these situations are not good for me, and I think I'm doing the right thing by staying out of them, but I can't help but feel that I'm being selfish and that I'm a bad friend. I really need to establish and enforce my boundaries, because that is a weak spot for me, but I'm afraid of going overboard and becoming too selfish and not doing enough for the people in my life.

Is this normal? Will I eventually feel less guilty about this? Do you think I really am being out of line? I know the details are vague, but I have an uncomfortable feeling about all of it.