There are some medical subspecialties that are more procedural, as well as some surgical subspecialties where you can deal with a lot of medical issues. As examples, if you want to do medicine but be more of an interventionalist, you can specialize in cardiology, GI, or pulmonary/critical care. If you want to do surgery but want to also deal with a lot of medicine in your practice, you can do things like surgical critical care, transplant, CT surgery, or vascular surgery.
I also was in the same situation as you -- forced to choose between IM and surgery at the end of my 3rd year of med school. It's definitely a hard decision. I ended up going into IM with plans to specialize in one of the procedural specialties, and am very happy with my choice. Having just started my pulmonary/cc fellowship this last week, I've been pleasantly surprised to find that the specialty is way more interventional than I had even expected. IMO it's a great specialty to think about for someone who has surgical leanings but doesn't want to be a surgeon.