Sounds more like you need a boyfriend who isn't going to be a liability to you, OP.

You need a boyfriend who is going to support you

Becoming a spinster is the least of your problems. If you commit to your writing, you'll most likely become a poor spinster. Or a creepy, transphobic billionaire.

Discourage him from having a girlfriend.

If you can have that kind of an impact with just a little poem, I'd say you're on the right track to become a writer.

1) if you want to be a writer, you have to be prepared for bad feedback of your work. Take the feedback that is right, and ignore the rest. That being said, this is not the case here. 2) Your boyfriend is a dick. All the time, even when you think it is fine. Dump him and go write. Per a professional writer

So one comment of a guy who calls himself your boyfriend already discourages you? You never have been criticized before? Dump the guy and move on.

dump him

You should never let someone discourage you from pursuing your passion! What you write is none of your boyfriend’s business. He clearly doesn’t understand you, your preferred genre, or how to treat people he cares about. I think that you need to have a serious conversation with him. If he belittles you or keeps disparaging your work simply because it “disturbs” him, you should probably consider leaving him. Also, you said that he “came across” an old poem—was he looking through your stuff without permission? That isn’t okay.

If you can’t think for yourself and/or be emotionally tougher, your writing probably won’t be very original anyway.