So, I don’t believe in “right person, wrong time.” Part of someone being the right person is coming along at the right time. So if the timing wasn’t right for some reason, it was the wrong person. And while a year is short as far as relationships can go, it’s still enough time to fall in love and imagine your future… you don’t need to invalidate whatever it is you’re feeling because your relationship wasn’t “long enough.” You’re allowed to have a soft spot in your heart for your exes.
That said, I agree that therapy would be a good move for you. Because yes, you need to get over your ex. If you quickly jumped into something new, it’s possible/likely you never properly dealt with the feelings around your breakup. And five years out, I also think you’re clinging to a rosy fantasy of your ex and the relationship you had, which I suppose I can see happening if you’re struggling with the relationship changes that have come with an infant.