LP gains and losses.

Depends on the game. If your team has higher MMR they should win so the LP drop is bigger for a loss, if your team has lower MMR they should lose so the LP gain is bigger for a win. IF it is really consistent that your LP for loss (like 9 times out of 10) is bigger than your LP for gains, then you are losing more games where your team is favored, and only winning games where your team is favored rather than when you're the underdog. In that case it's probably saying you're in a league where the average player is a little better than you and the loss over time should push you down if you stay at about a 50% win rate until you are at a level where you win games you're favored in and lose ones you aren't. (Or at least to where you do about the same in wins and losses when you're favored and when you aren't)