LP

Hi guys, my IGN is Cllau and I know that I'm not some kind of God at this game, as I have bad games too, but the majority of my games I'm over average. I'm wondering why do I get so little LP per win. I had huge win streaks, pretty good KDA in a lot of games but still no improvements in LP. I get like 17-18 per win and lose the same. My MMR is really that low and I'm not doing as good as I think or what could be the problem? I put a link there to see my history, or if it is not allowed that please search for my IGN and tell me your opinion. Thanks and good luck, summoner!