What to do about a frequent bucking horse?

My new horse is 4 years old. I've had him for a little over a month. I paid decent money for him and got him from a reputable source. Since I got him he has bucked me off once and bucked 2 other times. These aren't just playful bucks... I feel like I'm riding a bucking bronco in a rodeo. The first time he bucked me off, it was very sudden and I wasn't expecting it so I fell. The next time he went on a rampage. He started off with 2 littler bucks so I turned him in tight circles, and then once I let him go out of the circle and asked him to lope again he freaked out and bucked 4 other times. I'm talking MASSIVE bucks. Something just isn't right. The lady we bought him from said I could trade him in for another horse. But I don't wanna just give up. He is sound... he was vet checked. His teeth were just done and his saddle fits as far as I can tell. What is your best advice? Should I keep this horse or trade it in? Right now I really don't want to ride him again. I'm pretty scared. Thanks!