Running is not bad for you, but excercise that is intensive can raise your blood pressure and so if your heavier then is deemed healthy, its very important to get your doctor check you out to see if your able to take on intensive stuff. Also, high impact stuff when your overweight can put additional pressure on your joints and can cause injury. Be informed about what is going on in your body, its the best tool you have.
I'd say though- when you do get yourself into fighting shape that HIIT (High Intensity Insterval Training) seems to be the best 'bang for your buck', your workout intensivly for around 30 seconds, possibly 1 min at most- so intense you cannot go any harder. Your heart will begin to sky rocket and just as you hit the30 or 60 second mark, bring it all back down to a moderate though not easy level for about 60 seconds. Your heart rate will initially continue to climb and then drop to a moderate level, then repeat as desired. You do this for about 20-40 mins in total, its supposed to be very draining and if you can manage more, your probably not pushing yourself enough.
I do interval training, its a step down from this I think. I do try to put in as much ooomph as I can but I find I can carry on with a normal cardio workout afterwards and again the next day. I do interval training for 20 mins (just like HIIT above but not as intensive in the intense minutes) then move onto something like running or cycling, then go back and do another 20 mins.
If your looking to go back into aiding your weight loss without the impact, make sure you check your posture, it can feel infuriating not being able to work out as fast as you want to be if your not ready, especially if you've had experience of being able to do more. This can mean your head is pushing yo to work harder whilst your body is lagging behind, the first thing that you lose when in this battle is your posture. You lose your posture your at risk of injury and can miss out on much of the benefits of the exercise your doing. There is a right and wrong posture for each exercise, generally speaking, slouching is out, holding in your stomach is good, leaning on your elbows is out, head upright is good.
Try non impact exercises like cycling, the elliptical machine, the stair master, the arm cycle machine and weights. Lower your weight to a safer level and then try adding in running. Build yourself up to interval training or HIIT training after a few months, don't go into it cold.