have or has

[Camilla]

Hello,

I'm unsure which of the following is correct;

"My self-critisism and lack of confidence haven't been doing me any favours [...]"

"My self-critisism and lack of confidence hasn't been doing me any favours [...]" .

Instinctively, I would go with the latter, but it would make much more sense to use plural. I'd love some help as to which one is correct.
(I'm sorry if this is too trivial a matter for this forum.)

[Alan]

Frankly, I see no very good reason not to make it plural...