Mo, it is hard for me to weigh in on these kinds of posts because my first and obvious reaction is "You want it, you love it, you can afford it, get it." But knowing your situation with work and with the BF's recent objections to shopping, I recognize those factors need to be weighed in as well, and I don't know how to advise on that.
I've never been in the same situation myself since I've always had my own income, and we have separate finances. Honestly, I'm not sure how I'd handle it - I might not ever shop if I felt I had to . Lots of my married friends with joint accounts (whether or not they work) will say things when we are shopping like, "Oh, DH will have something to say about this!" It taps right into my own fears about dependence on someone else and having to justify my desires and feeling guilt - my OWN issues, of course, but making it hard for me to say "DO IT!" or "Don't do it!"
So I'll just say that I want you to have that blazer.