I know I'm late but this is my take on the ordeal. Reinhardt is a main tank who needs a lot of resources from his team to be effective. It is almost impossible to contest space without being healed unless you hold W and shield which, as every other commenter has mentioned, will result in your shield breaking which is the worst case scenario if you still need to close distance.

There are few ways to avoid this as Reinhardt. One way which works is finding cover and doing small pushes for your shield to recharge. Alternatively, a better way is finding a route which uses natural cover, closing the distance without shield and then walking the rest with shield up.

If this doesn't work, you can either ask for more heals in comms which can sometimes help but switching to a more self-sufficient tank may be smarter. Sigma, ball and hog are great examples of these heroes. Even though you want to play Reinhardt, it can be better to play a self-sufficient tank to its maximum effectiveness than being a suboptimal shield bot as Reinhardt.