It's been 4 months since my fut hair transplant and I don't see a difference?

Although some patients will see immediate growth of some or all of the transplanted hairs, most patients will experience shedding of the transplanted hairs and regrowth starting at 3-4 months after the surgery.It then takes a few months of growth for the hairs to develop enough length to start to be able to assess the result. By 8 months post op it should be possible to make an early judgement on the success of the procedure but the final outcome might not be achieved for up to 12 - 18 months after the surgery. 

Yes. Generally, after a transplant you will see all/most of your transplanted hairs fall out within the first month or two. From there, it's simply a matter of waiting for the grafts to start growing hair again, which is likely the stage you are at. Most patients start seeing new hairs sprouting around months 4-6, but it can occasionally take even longer. Don't be concerned about a lack of progress until about month 8.