I'm sorry you're having a miserable birthday.
But the day is young yet! I agree with the posters advising you to go for a coffee and a lovely cake and a magazine. If you have any friends locally, meet one /some of them for the coffee. Buy yourself a lovely bunch of supermarket flowers and put them where you will see them regularly. I love to have flowers in the bedroom on my bedside table, feels indulgent.
Buy a cake and put candles on it and have a tea party with dc when they're home - they LOVE this!
Given that it's a midweek day I would plan a very nice dinner - steak etc and a glass of wine for later. Or your favourite takeaway for dinner if cooking is not your idea of a treat. Start to spoil yourself and I also agree with the poster who said make a list of lovely things to do / achieve in the coming 12 months.
When dh gets home from work, run yourself a bath or a hot shower while he supervises the dc homework / bath / bed routine. Take some time out for yourself.
Then have a movie / box set lined up for when they are in bed.
And tell your dh that at the weekend you would like to go out for breakfast or lunch or dinner -whatever works best.
We don't always spend a lot of money on each other's birthdays but we do have a rule of infallibility for 24 hours for the birthday person - they are the focus for that day and night and we spoil them with small indulgences. It really works to make you feel loved! And mostly it just takes thought - a favourite dinner, run a bubble bath, pour a nice glass of wine etc
I hope your day perks up!