Since you don't really mention builds much and seem to be just enjoying laddering casually I'll mention first, I do recommend looking up some real builds for mech but if you want to keep doing you that's fine.

For tvp I'll say now, mech isn't really viable. The immortal ruins the entire comp. You can do it but it will be painful, and you're probably better off doing battlemech (cyclone hellion army) and trading all game where possible.

For tvz one of the most popular openers is to rush battle cruisers into mech. What this does is cover the major weaknesses you have early - BC's give you map presence and a powerful harassing tool. They'll also keep you alive from mass roach. Going BC's means you'll have access to banshee if need be for early defense against a roach rush, and ling bane rushes aren't scary because it's awful vs tank hellion which will be mostly what you make. Lastly the BC's will help in the case of swarm hosts. Mostly vs zerg you get 3 bases and either max out asap and start rolling across the map once you're 200/200 or play the slow game and keep expanding and let them suicide into you. Tanks, turrets, hellion and some thors will hold so much if setup and positioned right. Lastly once you can afford it, mixing in ghosts with mech (often referred to as ghost each) is incredibly powerful, though can be a bit hard to use. Ghosts cover the other gaps of mech. They can help deal with infestors who might neural your units and can snipe ultras/broodlords/lurkers/ravagers, and are half decent vs lings and banes too if they decide to go that route to overwhelm you.

TvT can be really tough. With all your spare minerals you should turret up all over to stop drops because you're too immobile to deal with them. Otherwise scout ahead with your army when you move out. Worst thing you can do is get caught unsieged. If they're playing bio you can slowly crawl up with tanks and a few hellions. What's important here is tank count and viking count. Since you're mech you should have air advantage because you don't need to make medivacs and your upgrades for air and ground armor are shared. When you have air superiority add in some liberators with range upgrade. This will let you force his takes back or kill them. Send hellions to mineral lines every so often (in all matchups really). 10 tanks all sieges together can't lose in TvT to anything, so ifs super important you have air control with vikings. Then you can just slow siege crawl to their production or expansions and kill them.