Relationships take A LOT of work

I've been with my guy coming up on 3 years. We've lived together for 2 years. We share a bank account. Our main arguments these days are about money. I feel like I can never bring up how he spends money, it always leads to an argument. For instance, I did earlier today, over the phone, and it led to a bad argument. He says I always bring it up at a bad time for a discussion, but I feel that every time I try to bring it up he feels like it's a bad time so nothing gets discussed or resolved. It's very frustrating. In long term relationships, I feel like it's ok to go throw short periods of not liking each other, because no matter what the love is there and it's strong. So for about 30 minutes today I didn't really like my boyfriend.