All the nurse could tell me is that he wants me to continue with the current plan of care (non-weightbearing NWB on crutches as much as possible, boot on when I'm up and walking around, cross-training
Thankfully my husband is a medical librarian and he found me this from Brigham and Women's Hospital Department of Rehabilitation:
"The lesion of MTSS is a result of a hypermetabolic state within cortical bone. Bone is in a phase of chronic remodeling as a result of persistent and increasing strain on porous bone.  Bone in athletes participating in running or jumping sports may have difficulty remodeling at a rate fast enough to adapt to the changes from mechanical loading. Ideally osteoblasts fill the tunnels left by osteoclasts, however in pathologic situations the porous bone inadequately accommodates to continued loading and microfissures may result and possibly progress to stress fracture.  It is know that the bone-remodeling sequence at the start of an exercise program commences approximately 5 days after stimulation and that the bone is weakened for the first eight weeks. Jones et al graded this stress reaction from normal remodeling (grade 0) to stress fracture (grade 4), with mild, moderate and severe stress reaction in between. 
The recovery time for periostitis or medial tibial stress syndrome is three to four weeks. Patient with stress fractures typically resume unprotected activities in 4-6wks and impact activities in 2-3 months. Adequate healing and the resolution of symptoms determine the rate at which the resumption of activities occurs with the impact activity. "
To me, this means that maybe things aren't as grim as I'd originally feared. Or maybe I'm just still in denial. Whatever, I'll take it.
Bottom line, I'm still essentially NWB through the weekend (and I actually asked for orders for one of those scooter thingies because the crutches are reducing me to a blubbering mess and fraking up my already messed up shoulder). I *might* be able to walk the 10k Mud Run on 5/20 but I'm not holding my breath (Please don't hate me Erin and Ali if I can't do it - I'm already disgusted enough with myself). If I could drop down to the 5k I would feel more comfortable going against doctor's orders and doing it. Not sure if that's an option though. I *should* be able to start training for Disney Wine and Dine in August and plan to run/walk it.
I'll know more after my appointment on Monday. Just keep thinking good healing thoughts (for both my tibia and my heart). In the meantime, I'm going to try to channel Dora and "Just keep swimming, swimming, swimming."