Diamond/ Platinum - Zerg vs. Terran - Widow Mine Problems

Hello! I'm Probe and if you haven't seen me before I'm a high plat, low diamond player. Now, getting it out of the way now, platinum league ZvT I have no problem with. I assume this is because my opponents don't really know what they are doing. However, low diamond and above I simply cannot win a match and hit a brick wall out of nowhere. 

Widow mines. I kid you not, I cannot beat them in the early to mid-game. While they are immobile and have a short range, I keep getting owned by Terran players who sit outside my third or second base with a handful of marines/murauders/widow mines, using the widow mines as ground control. If I try to push forward with my ling/bane the widow mines kill EVERYTHING. If I split the banelings I always find that the pathing of other units like zerglings and other banelings actually get in the way, making all of the banelings rub against eachother while splitting. This not only makes it take longer to split, but turns out it groups them up for..... Fucking widow mines. However, I think the most outrageous suggestion so many people make is when they suggest triggering the mine with one or two zergling. That is complete stupidity because any Terran player worth their salt will always kill the ling before it detonates the mine. So what? Overlords? That gets rid of resources and supply. That is a stupid answer for a unit that costs 75 minerals and 25 gas that can fire more than once. Plus there is always the chance the marines will kill the overlord before it triggers the mine as well. Mutas are useless as well because marines wreck their faces. Trading one or two muta for a widow mine is pointless. So I just outright die when the terran stims forward, shoots a couple rounds at a building or something, then runs back to the widow mines and splits. Eventually they just starve me out. Some maps like Foxtrot can be especially bad if you get worked into a corner. Let alone having to worry about the Terran getting smart and quickly sniping your detection. I just have no idea whatsoever how to beat this early game pressure. In fact, its not even pressure. If I am the aggressive player trying to deny a second base, one widow mine effectively shuts the whole fricken attack down if its placed behind like 2 bunkers. Any unit attempting to tank the shot of the widow will just get shot down. Run the whole army in, he targets the juiciest spot (which kills a ridiculous amount of shit).

Can anyone help explain what I need to do to not completely fail against this stupid unit? 

As a side note, I also can't seem to beat Turtle Mech. They sit on 2 base for a bit, make a shit ton of missile turrets for both bases, get 2 thors and tons of tanks, then slowly crawl forward and eventually manage to wrestle a third from me after like 5-10 minutes. Missile turrets prevent anything going into the bases for harass and after 3 bases have been taken, the terran goes mass Raven which literally shuts down almost every single ranged unit for zerg. Hydra, Corruptor, Muta, Queen, Locust etc.

This is like a last desperation attempt at learning how to win a single game against Terran before I throw my keyboard at the wall (lol) (but seriously I'm kind of going crazy here, struggling for months)

 Can anyone enlighten me to how you people do it? :/