Dear OP, YAdefinitelyNBU!
Almost the exact same thing happened to me, and it still rankles 17 years later. With me it was four months before my "landmark" birthday, and XH had previously said he'd like to mark it with a good piece of jewellery, so he gave me a price limit and asked me to choose what I wanted. I did, and he knew what I'd chosen, but hadn't bought it yet as, well, it was still some months away.
Then one day, while in one of those little old independent chemist shops in another town, I came across some bottles of my favourite perfume which was discontinued and I couldn't find anywhere else for love nor money. I immediately grabbed everything they had, and while in the queue to pay XH said, "I'll pay for that, it can be your birthday present". I declined, saying I thought I was getting the jewellery and anyway I wanted to use it now, but he was adamant that he would pay, and keep it for four months till my birthday. I didn't want to argue in the shop so I let him pay, but then he took the perfume and said he couldn't afford the jewellery now, so this was my "big" present.
When the day finally came I thought there would be some additional surprise like a diamond bracelet but no, it was just the perfume, handed over still in the chemist shop's paper bag. I guess we both knew that wrapping it would have been adding insult to injury.
So I don't think you need to get a grip, I know exactly how you feel. I feel insulted all over again just typing this. At least you got to use you gift now, and don't have to wait three months for it, but make sure he knows you are expecting the jewellery too!