I just hitched up my trailer, only 3000lbs, and I had such a Dip.
There is a lot to learn about trailer towing. Start by gathering data about your rig. You need "year, make, model" of both the tow vehicle and the trailer. Pictures are wonderful. Next check the sticker in the driver's door frame for weights. There are usually two stickers, one for tires and one for the rest of the vehicle. If it is a travel trailer, it too will have the weight information on the driver's side near the front.