Placing this in this section as it's to do with smoking cessation in a way but if I've got it wrong please move

I essentially stopped smoking about 8 years ago (for money and health reasons) and replaced it with nicotine gum. I guess I should be honest and say that the smoking itself wasn't an issue... but the addiction to nicotine and requiring it as a crutch (plus hating the withdrawl symptoms) is. I've been chewing the gum ever since and at this time I'm exceeding the recommended dose of 15 a day quite regularly (closer to 30): 2mg gum.

A bit stuck on this as I've conflicted opinions on the matter. I'm one of these people that if I know something has a high probability of causing me problems down the line then I'll try and curb it... but when I've asked (in a general sense) health proffesionals about adverse effects from gum they've been a bit evasive mostly due to a lack of study on the long term effects... (this being in the UK)

Does anybody know of any reliable scientific sources on nicotine replacement therapy (in long term cases)?

I just want to set my mind at ease and be self aware on what I'm doing to my body if it is in fact a problem... if that makes sense?

Thank you