This is a 'streak' or 'run' of tough moments. I had a night the other night with a 43% win rate for the night, although I am doing much better overall than I was when I was in your position. It is frustrating, though it's almost always something you can wait out. It'll turn around for you, though my experience has been that it turns around sooner if you maintain a positive attitude and focus on just learning more about how to play. I have had nights where I came out with a 20% WR for the evening, no matter what I did, nothing seemed to be panning out in my favor. Hell, most nights you can count on two or three 'carry' games where you never or hardly get to see any action before the rest of your team has mopped up all the bits and some nights you don't even get those as a form of 'salve' to the evening.
It's easy to come out thinking, "Holy cow, that was awful! I may just quit this damn game..." Do it. Quit for now. Take a break. Get your head straight.
Most folks who suddenly dip in performance are either grinding new units or are having trouble with some basic 'game mechanics' concepts that they think they understand better than they do. Also, sometimes, after a few good nights, folks will get a bit of 'confidence' in their abilities that are perhaps, unwarranted, based on a 'good run' of games that are conflated into thinking they are actually performing more ably than they might truly be on the whole.
This is just as 'dangerous' as can be the attitude that 'it's not me, it's them' when it comes to reasons why performance drops occur. Overconfidence leads to mistakes. It's an aphorism that in this case, happens to be true as often as not. The moment I think I really know what I'm doing with a tactic, unit, concept, it seems that is when I suddenly fail to do as well as I think I should -- or know I should be doing when compared to my stats and performance that I can objectively measure.
Even now, I am learning all manner of things -- or reinforcing the learning of them -- such that it ultimately will make of me a better player. I imagine I'll be learning new things until I either get bored or die, because that's just how I roll. I haven't been bored with this game even remotely yet.
Hang in there, man; and recognize that 'performance' metrics (ie: stats) are a Long Range View that are designed not to show everyone else how good or bad you are (even though there are plenty who will use them that way out of context) -- they are there to allow you to pinpoint strengths and weaknesses in your playing that might make a real difference in that 'performance.' Don't take them too seriously.
Another thing. When I first decided I was going to learn to play better, I did. In that time, though, there were times when I saw my damage per game, XP per game and credits per game increasing -- yet I was having my backside handed to me more than usual it seemed. This is part of that 'confirmation' bias that goes on. You have a bad run, but your numbers in all other respects are going up -- WTH?!? This is YOU doing better while your teams are getting rekt. Don't sweat it, it's not a horrible thing. YOU'RE doing better and that's the take away from all that.
In the meantime, while you're doing better, you're also just having a 'bad run' and it will ebb away as all things do. After a time of this sort of ebb and flow of your WR, you'll notice that those streaks are less often, less harsh and less annoying (in the longer view) than they currently are.
As an example, with a 1000 matches, every two or three games you drop or rise by a hundredth of a percent (.01%) maybe as many as four or five. In my case, a bad run can go .03 to .05% in a night, which is like, twenty losses more than wins or vice versa for a winning night. You don't say? A whole half a tenth of a percent, you say, wow, that's rough.
It's all about perspective. Don't let the stats ruin the fun for you, too, even when you're using them. I like to win. I like to do better. More than both of those, though, I really LIKE just playing the game.
I use my stats to gauge my performance over time and to help me spot my weaknesses and strengths in playing. Even so, I don't obsess over them (well, not too much, but I do like to look) beyond taking the time to see my improvements over time. Stats are for comparing. You should also compare your stats to then and now in order to gain perspective for your own peace of mind.
If you're going to let the negative moments intrude into your gaming, then using performance over time and your overall "fun factor" as positives to keep you motivated and invested with the proper amount of perspective will carry you through these moments where it feels like things are not going as well.
GL, HF & HSYBF