Need some advice and motivation!

So this is my before pictures, currently 14st 11lbs, I’m bmi classes me as obese, I’m 21 and fed up of feeling and looking so fat! I have joined the gym a month ago but keep finding excuses not to go. I am now suffering with lower back pain which I think is caused by my weight gain. I really need to lose around 4 stone. Please give me some motivation and some easy workouts that I can do even with back pain! I want to tone my tummy, bum and arms so any easy exercises anyone can give me? Also I currently only walk on the treadmill at the gym because I’m so embarrassed to run because I get so out of breath easily and I don’t feel comfortable using the weights there. Any help would be greatly appreciated! :)