Wishfulmakeupping if there is no fun in your life you need to introduce it. I think you need to be a bit more positive.
Presumably, you choose to have the kids and to do the study.
I've always felt a bit jealous of stay at home mums, I'd have loved to do it but we could not afford it. I work part-time. When the kids were little I had virtually no social life. It was quite depressing. Then I just told DH I was going to go out more, cheapish pub meals a couple of times a year, games nights with friends at their home or mine, coffee dates out, pub nights out. Yes, it costs money but not much and I found other couples I trusted and did a switch with the woman I knew in return for nights out, so I babysit her kids, and she babysits mine.
You can find the fun but you will need to look and you will probably need to make it happen. Plus if your kids are very small then Christmas gifts can be a doddle, NCT sales etc, and just a bit of extra posh food. Does your dh really need to do a lot of extra work to afford this? Or is he getting out of time with the kids and with you? Talk to him. There is no point in earning extra money only to spend extra money and feel miserable.
Together decide and priorities what you want, work, study, home life, just find the balance.
I cannot remember the last time I ironed anything.
Good luck, if you don't feel better when things start to change, please see your GP, it could be post natal depression. It is quite common.