You cannot gain 5 pounds of fat or muscle in a week and a half. the majority of that weight difference is probably water-related. Maybe you had a lot of sodium in your diet over the past few days. Aside from that, it is not very likely that you’re turning excess protein into fat. Protein is the last thing that gets turned into fat in your body, after fats and sugars.
If you are eating a lot of animal protein, there will be more fat in that. But if you are just using more protein drinks/mixes with not much fat in them, then its very unlikely that you’re turning any of it to fat. Some researchers say that athletes may need up 2.2g of protein per kg of bodyweight to maintain an anabolic protein state. In your case, that’s almost 200g of protein per day.
Just to give you an idea, an 8oz steak filet has about 70g of protein, and one 3-scoop serving of Grow! (now Metabolic Drive) has about 40g of protein. So you can see how much protein you’d have to eat to get too much protein. And from your other posts, it doesn’t sound like you’re sitting around doing nothing. With all the catabolic, aerobic activity you get through basketball, you’re probably getting too little protein if anything, unless you really are eating 3 steaks a day or drinking 5 protein drinks a day.
Don’t worry about such weight fluxuations over a short period of time. To really tell if your weight is significantly going up or down, you’ve got to get on a consistent diet, and you have to weigh yourself regularly at the same time of day and note a trend over a few weeks.
This way, you will know that your weight changes are not from water weight fluxations due to sodium intake, or from different amounts of food intake on a daily basis. For myself, for example, I know just one fast food burger and fries will add 2 pounds for me by the next day, but its gone a day or two later. Just water weight from the sodium.
As far as the strength increase goes, it could have been anything from better sleep the night before, better diet, better energy, etc. As others have said, in a week and a half you probably haven’t gained all the muscle necessary to translate directly to that kind of a strength gain. Its probably a combination of neural adaptation and better energy that day.
To really know for sure if you’ve got a strength increase, you have to have a consistent weighttraining program, and you also have to log and keep track of your progress. From week to week, you may have fluxuations of a few pounds here and there. The important thing is to notice an upward trend over a month or two of training.