If someone I was dating gave me that ultimatum... I'd tell him to not bother waiting until April and I'd sign him up to Tinder myself. The flatmate seems toxic and if your boyfriend is issuing these ultimatums this early in the relationship, what is he going to start dictating to you when you're living with him? That's how the cycle of control works and once you're in that cycle it's hard to get out of. I'm sorry if I'm overstepping the mark by saying this but I've been there, I think you need to look into finding a new circle of people to associate with who are more positive and understanding of what you want/need.