running, running, running and can't lose???

Really hoping for an answer or suggestion. I started running on a treadmill about 10 months ago to lose weight. I've been at my current level for 7 months now of 5 miles (in one hour) four times a week - supposedly burning 750 or so calories each time. I'm not eating any differently except that for several months I had cut out the one regular Coke I had every day and I've not lost a single pound NOR do my clothes feel any looser at all. I've really tried to stick with it thinking that sooner or later it would "kick in" but I'm getting really frustrated at the total lack of results. Any suggestions?? Thanks in advance.