The problem is your weight. You shouldn't be struggling until the third set. Don't worry about low numbers, it'll increase. You should also work some strength into that routine. Typically I do a 10 x 3 followed by a 5 x 10. If you're still new, I'd go with a 5 x 5 (or 8 x3) and your 3 x 10. Just remember to select the weight that's right for you. The last sets should be where you struggle. Hope this helped.
Also, remember appropriate rest periods depending on what you're doing. If it's low reps at high weight, typcially 2-3 minutes is fine and if its high reps at low weight, around 60-90 seconds works too. These guidelines aren't specific, but try not to exceed them. If you feel you can recover with less time and still give the same effort, then do it!