Hello Friend
When I started at a little bit higher weight then you, I started on the elliptical and even doing 5 minutes sucked! I was having trouble breathing and I just hated it. But I stuck to my guns and did about 30 minutes a day for 3 days a week. I slowly increased my time and resistance (started at 1!) over a couple of months and was doing 60 minutes on resistance levels that varied, but up to 10. Now I only do treadmill running because my shins have improved over time and have strengthened enough that I don't want to be on the elliptical....the main thing with this is to take your time!