I think there are a couple questions you need to ask yourself - the first is why is it hard for you to be alone? You're the one person you're stuck living with for your entire life - it shouldn't be hard to be alone with yourself. That's where it began. That's where it will end.

You mentioned you have a therapist - this is something you might wish to explore with them.

The second question is related - what are you looking for in the "not alone"? What do you want? What would bring you peace? Are you looking for a relationship? A friend? Sex? etc? While you have to be comfortable with yourself, part of that comfort is knowing and being confident in what you're looking for. It may be that the world won't or can't provide it, but that's why I put this question second.

The final point I'll make is that there's nothing stopping you. You're an adult... within the constraints of the laws of your society, you CAN do what you want and there's nothing stopping you. It may not go the way you want, but it might, and wouldn't it be fun to try?