What should I do?

If this is important to you and a deal breaker, then you have to leave. However, many vegans I have known do have non-vegan partners. For those that are bothered by meat cooking, they ask their partners to have their meat meals at separate times.

Wait! I thought you were engaged and attending weddings?

One has to get adjust,if he says to accept him or leave then just wait this might be one of the reason for him to get away, just check his behavior if this is the only reason then i would suggest to accept him

I think you can work this out. There are actually many couples out there with the same situation. The one is vegan while the other is not but they still manage to work out their relationship.

I know it's hard since you've been together for a long time and all those time you thought both of you will be vegetarians forever, but people change and so is their preferences. You should try and accept it although I find it unfair that your boyfriend demands it.

Just talk with one another and understand each other. Let him explain his side and listen then explain yours and make him listen.

If you can't adjust with non-veg then leave him. Before that talk to each other