I don't think it's harder, maybe it's just because you're more suited to a 1st POV format? I don't think the fact that the story being affects the difficulty as well, unless you dislike and you're forced to write it lol. My suggestion is for you to start writing third POVs in the future chapters, or just a couple of chapters and update them. Then you can ask your readers if they like the recent update's style more than the older one aka the first POV! If they prefer the third POV, then you can finish the whole story with that, and then edit the earlier chapters with a third POV. However, if they ended up liking both, then I suggest you mix it up, like starting with a thirs POV then go with a first POV afterwards in one chapter.

It's all about what you're comfortable with, really. If you feel restricted when you're writing something then it might be from lack of creativity, which ofc can be attained if you perhaps read more? I'm sure it can inspire you haha. That's just what comes from me tho, it all ends up on what you feel is best! Best of luck ^^

It's not necessarily harder, it's just more common to use 1st pov with a btsxyou btsxoc fic. But I've seen enough 1st pov bts memberpairing fics that also sometimes just throw a pov in there because they want to express that one character's feelings better. It's all possible. You can either change the whole story, start on 1St povs from here on or just throw a pov or what in there :) good luck with writing! ^^

You have a lot more opportunities if it is 3rd person rather than 1st......You can do a lot more without being limited so I say stay with third

Third gives you wider spectrum to talk about their feelings and stuffs

Boyxboy doesn't make it harder to write in 1st pov...it's just harder in general because the pronouns get repetitive and you have more restrictions

Bts x you would actually be 2nd point of view, which is honestly hard af to do. 3rd and 1st are easy, don't sweat it so much. All you really need to do to change the story to 1stpov is to take one character, and make that character tell the story. Use words like "i, me, and my". Pretend to be that character and write the story based off their opinions and feelings so that your are effectively telling it from thwir point of view.

How is the pairing going to make 1st person pov harder just because it's gay? It's literally so much easier when you have two different pronouns for your main characters which you will have with a 1st person pov. I don't know who told you it should be harder to write gay in 1st person pov than in 3rd.
That said - I personally don't like 1st person pov and it is - generally - harder to make a good character in 1st person. It's hard to stay limited to that character (it's a little like writing 3rd person limited) and writing limited is harder than omniscient for many people. (Not that in particular find omniscient easy either).

You could try and edit a chapter and see if you like it or not. Get a feel for it. Decide afterwards. Don't let your readers decide this for you. If you end with a pov you find hard to write, you most likely won't be satisfied with the story.