I'd rather see an athlete doing a less bodybuilder-like split. The body rarely ever functions in isolation, so training it in that manner is not optimal. The two best options in my eyes would be a 3 days a week fullbody, or 4 days a week upper lower split.
Whichever you chose, focus on these exercises:
Glute Ham Raises
Bent over rows
(forget the bench press machine, just stick with dips and pushups for your chest and triceps).
Each workout should be made up of 6-8 exercises each performed for 3-4 sets. You want to have at least 20 total sets and 32 sets at most. Any more than that and you'll see the effects of overtraining. Reps can vary from 3 or 4 on the low end, all the way to 15 per set on the high end. Obviously the reps will be closely correlated to the weight. You want to be able to complete the set without going to complete concentric failure (ie. I can't physically do anymore). If you can complete the set easily, then add more weight. If you can't finish the entire set, remove weight before the next set.
The main thing you need to remember is to work harder, not longer or more often. 5 days a week is a lot of time to be in the gym. Your body needs time to recover and rebuild itself bigger and stronger. If you are constantly taxing the system, you'll see less recovery. That does not mean, however, that you should be avoid lifting heavy and having extremely difficult workouts. This is just a better way to get the strength results you want.
But the biggest factor for weight gain is nutrition. You can have the world's greatest workout, but it would be a waste if you dont get enough calories and protein in your diet. Whatever you are eating now (try to get a rough idea of total calories per day) you need to take that and add 500. Eat often, 4-6 meals a day. Eat lots of lean protein and veggies. And try to stay away from overprocessed foods and sugary items. At 150 pounds, you should be eating 115 grams of protein each day. Keep track of how much protein you eat tomorrow and saturday and see how much you need to add.