It's just hard to understand what is going on.
There is no clear plot, just things happening. Suddenly it's fantasy, vampires appear, vampire hunters appear... why, what are they doing, why do they hunt the girl? Many characters just pop out of nowhere and there are no explanations why they are here and what do they do. What was the reason his brother left? So many questions, zero explanations. You keep adding this idea and that idea, werewolfes, time bubbles... Still no plot is actually happening and they do nothing.
You claim it's shounen ai, but... it's not really? Well we have characters feeling love for each other (kinda?), but it's not a shounen ai, because nothing is happening between them. They are just "ah, who is she\he for you, you're mine only" and that's it. The dynamics of characters is unclear, we don't see them doing anything together (like Luccio and Kleine), so why are they... together? Did they become friends? And how did this happen? I have no idea, because it didn't happen in the comic.
In the beginning, I was going to say that the art is pretty solid (and it is), but it doesn't progress in the course of 4 years, you mostly just show faces, a lot of eyes and bodies up the waist. There are no backgrounds and no establishing shots. Where are they? School, bedroom, mall? Is it day or night?
Also, it's pretty hard to differentiate female and male characters. And just characters altogether, they all have the same face and body structure. They even have the same hair sometimes and it doesn't make it easier.
Overall the main problem, I'd say, is the lack of plot. With your level of art you definitely can draw better and become more popular, people on Tapas do love BL and fantasy and anime style. But you still need a more solid story.