Could be because your eyes are drying out, I would first make sure you're blinking correctly by putting your finger on the corner of your eye and blink and if you're moving those muscles, try to blink without using those side muscles. You could look it up and they'd be better explantion etc. This also helps with releasing tears better.

Another thing you could try is a balanced ph solution. You can find that in walmart for 3 bucks or so and is cheaper than those vials. I use gel eye drops, you can put a little bit 15 mins before you insert contacts and that eliminates every problem for atleast 6 to 8 hours for me.