I think that the fallout you are experiencing is what BF was afraid you may experience

I'm so happy that you went to the concert! And I'm proud of you for finding the strength to go!

It's not an uncommon to feel let down after something that you really look forward to, or build up in your mind, even if you have a wonderful experience. I think that the best way to combat these feelings that you are having is to try to make some kind of plans so that you can have other things to look forward to in the future... even if it's only a trip out to the mall, or a nice lunch out. Or you could otherwise try to fill the emptiness with other things such as reading or binge-watching your favorite shows (((HUGS)))

I'm sorry that you are feeling so down
How are things going with your meds? Do you feel like they are helping at all?