If wearing a helmet is the difference between you having the confidence to cycle (or to cycle more) or not, you should wear one! The health benefits of cycling outweigh greatly any negative consequences of helmet use.
On the other hand, if wearing a helmet makes it likely that you will cycle less, then the balance of advantage is cycling without a helmet.
If helmet wearing is unlikely to affect the amount you cycle, you may like to consider the following. Interpretation of the data can be controversial, but examination of the wider evidence from places where helmet use has become significant suggests that the following are reasonable conclusions:
In all cases you should regard learning to cycle skilfully as your most effective defence against injury of any kind.
Note: Reference to choice in wearing a helmet clearly does not apply where helmet use is mandatory.
Erke A, Elvik R, 2007. Making Vision Zero real: Preventing pedestrian accidents and making them less severe. TOI, Norwegian Centre for Transport Research Report 889/2007.