The stag clashing with my birthday wouldn’t bother me too much - it can be difficult to arrange these things with dates that suit everyone and I’m not sure a partners birthday, unless a milestone one, would be a big reason to ask for different dates.
I’d be annoyed by the fact it’s basically a weeks holiday he’s going on!
sounds like he works hard and puts many hours in, I wouldn’t deny him a break but I think 5 nights away is selfish especially given that you have a baby and debt.
i’ve declined hen weekends of good friends in the past as I couldn’t afford the cost of fancy 4 day breaks abroad, nor justify it when we had kids to look after and limited childcare help or annual leave (never been the maid of honour though so didn’t have that added pressure or guilt of feeling I HAD to go)
but there would usually be an extra date arranged for a second hen, just a local night out so everyone could still celebrate but without the commitment or cost of a weekend away.
you said he helps out friends and family on weekends, will try and work more to cover the stag expenses, didn’t want to cause more issues with the dates so sounds a little like he doesn’t like to say no to people or feel awkward speaking up (I could be reading this comeplety wrong) and so it feels like he’s prioritising others over your feelings?
you have a young baby who wasn’t planned, finance difficulties, and a partner you don’t get to spend much time with now he’s increased his workload and so I’m guessing your relationship has changed a lot to accommodate this and I get that wanting to spend some time together even just at home would be nice, and sounds like it doesn’t happen often if this is something you have to plan as a birthday months in advance so I would feel frustrated that it appears so easy for him to just be able to find the free time and money for 5 nights abroad. I’d probably feel more generous if it was a 2 night away stag. I’m not sure why anyone needs a 5 night stag or hen trip though so maybe I just have different thinking.