If you are taking the RX 50,000 IU D2.... you most likely will not see much benefit. This form does not work basically well at all.

If you are taking D3 OTC...what dose are you using?

Vitamin B12 cyanocobalamin shots only stay in the blood stream for 72 hours. It would be much more effective for you to raise your levels orally, using 5mg Methylcobalamin (the active form) on an empty stomach daily. Within 3 months you will see high serum levels.

I'd get a B12 test run at least a week after your last injection to see what your blood level is. If it is low, then your injections are not working for you.

Methylcobalamin is OTC and pennies a day. Mostly available online though, but not difficult, dangerous, or a hardship in any way and is far more effective.

Many doctors don't know what methycobalamin even is, and don't understand oral works.

Here is my B12 information thread...
http://neurotalk.psychcentral.com/thread85103.html

If I were you I'd study this carefully and fix any B12 issue you are currently having and perhaps your gastroparesis will reverse if it is in early stages. Delay, and it may become forever.

Edit to add--- if you are low in magnesium Vit D often doesn't work.
Here are the cofactors needed for successful Vit D absorption and utilization:

magnesium
zinc
vitamin K2
boron
a tiny amount of vitamin A

Vitamin K is in green leafy veggies, zinc may be depleted by some drugs, but is in most animal meats, boron and Vit A are in most multivitamins. But magnesium is often low in Americans. So consider that too.
Here is my magnesium thread:
http://neurotalk.psychcentral.com/thread1138.html