is bike fit / seat height proper ?
what gearing does your bike have ? chainrings and cassette ?
the average 5-5 @ 200lbs plus person will not be a gazelle up the hills - so good chance you will need lower gearing to compensate
spin and take your time - don't push too tall of a gear - especially on long climbs ... bad for the knees ... you will need your knees when you get older