Can't increase milage

Hi! I can’t seem to increase my milage passed 3 miles. I get calf pain and just don’t feel like my body can do it (I can breathe fine). I don’t like the Galloway method as it’s difficult for me to run again after walking. I’m a washed up athlete so I’m not new to running but I’m new to running without any other activities (I played field hockey so I had a destination). I am running the NYCruns Brooklyn half in April and have a training plan but not sure I’ll physically be able to do it.