Perfectly Natural to be nervous of the bumps. I used to be the same when i was learning, Almost petrifed to let go of the controls. This was in fact part of the problem becasue i tried to correct the bumps, Much better to let the acft do its own thing (within reason!).
When i Instructed what i did was take control of the acft and remove my hands from the controls and let the student see, that you are unlikely to flip roll in 1second.
As you spend more time in the aircraft u will get more confident and comfortable, Talk to you instructor and tell them your worries and they will help to reassure all is well.
Good Luck!