How many endings are there? I recently finished the game and felt like there was more to the heaven and hell part because there was still a mirror for Limbo but it wasn't activated >:T

Don't worry, it's not supposed to be. Anyway, there's three endings, not much can affect the possibility of getting either one
If you want, I'll go ahead and list the endings

Please do!

Oh no.... Sorry, I never got a notification of your reply, are you still wanting a list? It'll seem a bit disappointing with all the wait for simple endings
There's no officially set "neutral", "good", or "bad" ending

With the bleeding symbols, you can choose to activate it or not, doing so will make the different areas each deactivate/erase one by one, and if you have all the flowers, Limbo would automatically use them to activate the erasure of his own existence, but if you don't have all the flowers, then you have just trapped him with an entire world of nothing left in it. The other ending forces him to step away from the Bleeding Symbols and walk into an endless void just like in the start before he found these different areas in the first place