Maybe you are just pushing it a bit or mabe you indeed made a mistake. I checked the Coachman web site and couldn't find a Sprit witha 4550 weight (I assume it is dry weight you are talking about) but there were several LT models. What exact model did you buy? Is it a travel trailer? The fifth wheels are all larger and heavier, as far as I can see...
The Dry Weight of a trailer is usually a fiction - most models have optional equipment and feaures that are not included in the dry weight. Awnings, for example, are often not included. And then there is the probability of some water onboard (water is 8.4 lbs/gallon!), some propane in the tank (about 4.5 lbs/gallon), etc. So chances are your actual trailer weighs somewhat more than 4550 even before you put any gear in it. And you wil be surprised at how quickly the weight adds up - everybody is!
You have probably also learned that your actual tow capacity is almost always less than the rated maximum. Anything you carry in the truck, including passengers, must be subtracted form the tow capacity. Even the weight of the tow hitch is subtracted frm the max tow capacity. The
2003 Ford Tow Guide shows a 10,000 lb GCWR for a 4.2L V F150. The max tow is 5400 lbs in the Supercab with 3.55 axle and only 4400 with the 3.31 axle, so I hope you have the 3.55. Please check that immediately if you are not absolutely sure!
So you are certainly close to the limits, if not beyond, so a trip to a weigh station is a must. Weigh the truck alone (but with the expected amount of gear and people on board) and then weigh the truck and trailer, axle by axle and total. The total weight will be one critical factor - it cannot exceed the 10,000 lb GCWR. The weight on the truck's rearaxle is also crcial when you are near the max. You can find public scales a many moving van companies, grain elevators, field mills, stone & gravel yards and truck stops. Prices are usually very reasonable, especially if you don't want an official weigh ticket. Should be around $10 or maybe $20, since you want two sets of weights (truck and truck + trailer).