How do you prevent clumpy eyelashes?

Start With a Clean Slate. Make sure all traces of your makeup from the day before are gone, any leftover or flaky product will create buildup that prevents a smooth application. 

Always Wiggle Your Wand. Hold the brush at the root of your lashes and wiggle it back forth as you make your way to the tip of the lashes.

Never Pump Your Wand. Don’t pump your wand in and out of the mascara tube, this injects air into the product that will speed up the drying out process, which creates clumps. Twist as you pull out the wand instead to get an even amount of mascara on the applicator.

Know When to Toss Your Mascara. The shelf life of mascara begins when you open it, and it’s best to toss the old tube and buy a new one after about three months.

Try No to Overdo It. When it comes to coats, stick with two as a general limit, anything more will weigh down your lashes and start to give you that spidery look. Always let the first layer dry for at least 30 seconds before applying another.

Don’t Add Water. If your mascara is drying out and hasn’t reached its expiration date, try soaking the tube in a cup of warm water. This will help soften the formula and make it less clumpy, but it won’t dilute it and will allow you to use every last bit.

Apply less mascara at one time and let it dry between coats. Use an eyelash comb or eyelash brush to separate the lashes after applying so they dry seperate. And no more than three coats. After three all you are doing is gunking the up the lashes. And it's possible your mascara isn't very good. Not all mascaras are equal, some are fantastic and some are clumpy and gunky. Look up mascara reviews on line and see if what you are using is a star or a fail.