How to stop being on Tilt?

This somewhat goes off my last post, and I'm at a point where I have no idea what to do anymore to stop being on tilt or improve in ranked play. I was doing so well for awhile. I put in times watching pros play, I watch lcs (for fun and to learn as well), I've spent time practicing farming, and learned to play all the roles. When I first hit level 30, I only mid/jg/ and basically Fiora top ever, and that's all I could do. Couldn't farm, had no idea about objectives, and was a typical bronze player. I've put in all of this time, and work to try and be better. I stopped ranked for a few months and just played tons of normals. Played a ton of adc and sup games to now the point I'm a passable adc, and support is arguably my best position. And for awhile, it worked. I was at 70 LP bronze 1 (which was an improvement, and so close to being out of bronze), and then it happened. The worst losing streak of my life. I'm now 2/14 out of my last 16 games. My MMR was ridiculously high before that, and I was getting like 30 LP for wins in some cases. I don't know how much I'd gain now because it's been awhile since I've won in ranked. I'm losing like 14 LP per loss now.

I don't know what to do. I didn't even feel like I was on tilt in the beginning. I was winning my lanes, being positive (the DST method), and trying to improve my self as much as I can. And at first, I was just losing close games. I'd try my best, usually do fairly well and the game would be close but they would have the slight advantage, and then one of my teammates would get caught out or something 50 minutes in, and then gg. I didn't think anything of it at first, but it just kept happening. I just kept losing close games. Most of the time I'd win my lane, or if I was jg I'd try to get my laners fed, but some lane gets rolfstomped, or I have a game when I'm jg Amumu. Right as I get to level 3 and go to gank, literally all 3 lanes die at once. Gg.

I'm not trying to blame my teammates for my streak. I'm just as at fault some games. Played a game as zed (my fav champ and the only one I actually have a skin for) and I fed hard and cost the game. I've no problem with admitting when I'm at fault. It's just these games that I feel like I should have won or I played well enough to win get to me, and just put me on tilt. I didn't even realize I was until 7 losses in, and figured I thought I was playing well so maybe I just got unlucky and lost a few close games. Now I'm just playing awful, and don't judge how I play off these last few games. I don't know how to stop being on tilt.

I tried just playing normals. Normals I don't even understand. I'm constantly ranked and placed with mid silvers. 4 and 5 whole divisions above me. And I do well. I'm not overmatched, keep up my farm, and win more often than not actually. And I usually do way better. It's like ranked is a totally different more stressful game to me, and I just do horribly recently. I don't even find ranked fun anymore.

Anyway, advice would be very helpful. I'm just disappointed and and don't know what else I can do. I feel like I've put in a lot of work to get better and now I'm worse off than I was when I wasn't caring at all. Thanks in advance.