I become very weak after fasting. If I cannot make it to services, is it more important to fast than to be in services or hear the shofar?
I am assuming that you mean the services and the bolowing of the shofar after the Yom Kippur services.
The most important part of the day is the fast, even if it means that you will stay in bed all day and not pray at all. As a side point the shofar at the end of the services is not an obligation rather, it is a symbol that the holiness of Yom Kippur has departed, but there is no obligation for one to hear it.
Have an easy fast and a gmar chasima tova