This is both a tough question and really easy at the same time. The TLDR version is: talk to them, see what their feelings are on it, and see if you can come to a solution you’re both happy with. Maybe you won’t even need to change anything. Maybe it will turn out to be a huge deal. But that should be a result of what’s between you and them, not pressures from tumblr social justice activist types, y’know?
The long version:
I have certainly known of genderqueer and trans people who have been very hurt by partners refusing to identify their sexuality as something compatible with dating a person of that gender identity. A lot of people I know who I would have called “bisexual” identify themselves as “pansexual” instead, for pretty much this reason, and that is great. But in my own opinion and experience, labelling sexuality is something that’s pretty personal and flexible. For example, I’ve read a few very touching stories from women who were totally straight, except that the love of their life turned out to be a woman. The only woman they were ever attracted to. Should they change what they call themselves at that point? Are you bi if you are attracted to men your whole life and then ONE woman, who you marry? Eh, I’m not going to dictate. Up to them.
Similarly, I’m bisexual, and have had a couple of people say in a hinting, condescending tone - “Don’t you mean pan?” Nope. I’m bi, cheers. That doesn’t mean I’m transphobic, any more than straight people are automatically homophobic. It doesn’t even mean that everyone I’ve ever or would ever be interested in is cis! I’ve had a bit of a flirtation with a trans man - who is definitely a man. Wouldn’t it be a bit offensive if I said to him, “well, I think I’ll identify as pansexual now, because you’re not really exactly female or male, and I need to reflect that in how I identify myself?” No, I’m not going to do that. I know my own sexuality best. You know your own sexuality best.
What I’m saying is, I guess, it is great that you are concerned and questioning. But don’t feel that you need to change the way you identify yourself just because of general social pressure, or random people who think you’re not being respectful enough. Especially tumblr people. We have a tendency to disappear up our own arses, let’s be honest.
The best thing to do is really to talk it out with your partner and see how they feel about it, because yeah, there is certainly the potential for it to be iffy. But there’s also the potential for it to not be a big deal at all, and it’s your partner’s opinion and feelings that determine that. They’re the person who will best be able to tell you whether you’re disrespecting them! If you talk it over and they don’t really give a damn, great. If you talk it over and they feel like you calling yourself “gay” is defining them as exclusively female, it sounds like that’s something you’re open to working out with them.