Not getting committment from my MARRIED PARTNER?

Please help me. Please help me. Today is my 36th birthday. I'm a female and am in a relationship with a 50yr old man since i was 26 - 10yrs ago. Hes the love of my life but i feel i will have to finish the relationship. I have so much as a result of our relationship, i drive a top of the range car, i own an apartment in Chelsea and i eat in all the best restaurants. But today i'm eating alone and at this point i envisaged us being together as one. Right now, i'm all on my own celebrating my birthday ALONE. Because he has to go and accompany his wife who is receiving some crummy award for her charity work. Then he is coming back here for ONE hour in the evening before joining her for DINNER. I feel sickened. I feel that i am second best. This time, i got an envelope with a card stuffed with cash - NO thought or special consideration afforded to my gift. The gift is saying nothing about what i mean to my partner on an intimate and sacred level. Please help me. I've worked my way down through my bottle of bollinger and tonight i feel like gate crashing his special dinner as another man at work has been constantly begging me for dates and I'm going to bring him to the same restaurant at the same time, to TEACH my partner a lesson. Any thoughts