Get out of family event - how do I get out of this without being a jerk

Many of my in-laws are in town. Sunday is supposed to be a family get together that’s turned into a baby shower for my brother in law and his wife.

I am depressed. I am tired and I don’t have the energy to be happy on Sunday I just don’t.

My husband is supportive of me not going - I just need an excuse. One that doesn’t make me look like a selfish jerk. I wish a simple migraine would suffice.