All these MMCs aren't you.
They were never you. So therefore you helping
them romancing the girls is the ultimate form of NTR. Think about it. But jokes aside, treat it as a story experience rather than a self insert, and you will be fine. We all have our preferences, and there is nothing wrong with them, however experiencing something new from time to time is also nice.
That said, there is a game called
Another Chance in the catalogue, it's very similar to Uni (but not entirely) and with a male protagonist. I do like Chelsea better than him though.