Wtf? Am I over reacting?!

Okay so here it is, my birthdays coming up in a month and this is the first year it falls on the weekend since I can even remember, so I was sort of stoked to do something on my actuall birthday since I never get to! Anyways, so we’re at my in laws today for Father’s Day and I mention the idea on having everyone over to our house for a bbq and then I proceeded to ask, maybe after the bbq you can take the kids (my step son and my daughter) back home for a sleepover so this momma can have some much needed fun. My MIL then says, well we’re watching SILs baby because her and her husband are going for dinner... on my birthday they decided to utilize the only baby sitter we have and make everyone unavailable to even come to the bbq. They know when my birthday is, like I can’t even sit here and think of myself doing that on one of their birthdays, its just rude. They know we wanted to do something, so like why?!? Every occasion I’m present and always the one helping set up, clean up and attend. For every fucking birthday I go above and beyond for these people! The weekend before my SO’s birthday they had their mom watch her daughter then the weekend of his birthday, had their mom watching their daughter and THEN the weekend after his birthday, guess what? They had their mom watching their daughter so they can go out, AGAIN, for the THIRD TIME so by the time the following weekend hit, I obviously didn’t ask my MIL to watch our kids because they just had the last 3 weekends baby sitting so I felt bad. This always happens, birthdays, New Years, Valentine’s Day. Anyways, so I kinda just said to my SIL (nicely of course because maybe they forgot) that I was hoping to have a bbq that weekend for my birthday and was hoping to have the kids stay and grandmas for well, a break. She says, we want to go for dinner that night and have my mom watch our child, so that won’t work. I was just blown away, can’t they have a dinner date the weekend before or after? They have every weekend available to do something so why this weekend? Then I remembered, They abso-fucking-lutey know what day is my birthday, so it wasn’t a mistake. An hour prior they were saying how excited I must be to have my birthday on a Saturday... so I mean, come on! Am I overreacting for being hurt by this? I never said anything but still, it’s sitting on me heavy.

Side note: they don’t go out every weekend, only the weekends that are occasions or that they know we’d like to do something ie: our birthdays.