The horse is QH and loves jumping himself.I only have a wetern saddle.But can I jump with it?

Ah, a rider after my own heart! I jump English, Western, bareback, and sometimes without the horse (but that's not a good thing).

Yes, you can jump in a Western saddle, but be forewarned that 1) you want to keep the jumps low (2 feet is probably the max you should attempt) as you can't lean forward enough to balance if there's a horn in your way, 2) Western saddles actually distribute the rider's weight more evenly, so your horse might actually enjoy it, and 3) you'll need to be extra careful about the position of the saddle in relationship to the horse's shoulders. If he can't move his shoulders freely, you're going to risk hurting him. English jumping saddles are specifically built to avoid interference with either the horse's movement or the rider's balance. I find I tend to stay more-or-less upright going over cross rails in a western saddle, so I have to be careful not to land on the horse's back with a painful thud.

You don't say whether you're male or female, but I will share that I learned the hard way that a barrel saddle is an excellent choice for its small size and light weight, but that tall, skinny horn that lets you grab with your whole hand will very neatly slip under the front of your bra if you lean too far forward, which can lead to some very interesting riding experiences. Just keep your palm flat on the horn to prevent that and to keep the horn from breaking your ribs or jamming into your solar plexus on the up side of the jump arc. If you're a guy, you have another body part to worry about as the swell is unforgiving on landing. Okay?