I am sad that my bf and his mom want to go on vacation together, but not with me included

first some background info, me(21) and my bf(22) are now 3 years together, we know each other for 5. Before we started dating, he went on a few vacations with is mother. Just for some bonding time, nothing special or weird about it. In the first year of us dating, they went to Greece. I was very happy for him and was excited about it. after that they never went on any vacation together anymore, not on purpose or anything, just because.

So the thing is that i dont have a mom anymore. She killed herself in 2017 and i have been in foster homes since then. I have a very big family but no contact with any siblings or my father. This is because they are a really bad influence and its very hard to not have contact with them, but its better for my mental health and for me emotionally. When i do have contact, there are always fights and negativity and they have never supported me in anything. I got 2 diplomas and there was nobody of my family there when i needed to collect it, which breaks my heart because i really am a family first person. I am going to therapy now because i had a very rough childhood with my family and i still have trauma that i need to work on.

In 2 weeks, we are going to Bulgaria for 9 days, i was very excited about it but the question just trowed me of guard. So what happened was that his mom came over for dinner and she has 2 dogs. Because we live in a building with no elevators, she has to carry them up the stairs. Dinner went very well and everything was going fine. When she was leaving, my bf kindly said that he would carry one of the dogs for her off the stairs and that he would walk her to her car. I said my goodbyes and waited for him to come back. So when he came back he just instantly asked: "is it okay for you if i go on a vacation alone with my mom?, sometime".

And i instantly just became sad. And i feel very guilty about it. I asked why he asked and he said that his mom asked him that when they were walking to the car. I think thats more sad because i dont understand why she couldn't just ask him when she was having dinner with us, but that aside, i DO want him to go on a vacation with his mom.

I am just a bit sad that they never asked if i wanted to come along. When i asked if i maybe one time can come along he said no, because then his mom will be a 3th wheel. and i do get that, but its also the thing that i am jealous because i can NEVER go on a vacation with my parents. And no thats not a excuse for him to not go on any vacations anymore with his mom. But i also feel a little left out.

-I am not saying that i should come along EVERY vacation with them, but i think it would be nice if they sometimes would invite me too.

-We didnt get into a fight about it.

i swear i do feel guilty, and i said to him that he can go with her whenever he wants to and thats okay with me. But i am sad about it and just need some honest opinions.