You came here looking for advice, and I'm seriously concerned about some of the advice you are being given. Obviously it is your choice, but please do not listen to the people who say tanning is safe if you only do it 2 - 3 times a week. It is NOT. In fact if you go to the website below you can read about a girl who got skin cancer at the age of just 21 from using a sunbed twice a week.
As I've already said, even using a sunbed just once can increase your chances of skin cancer. Using a sunbed once a month, can increase your risk of skin cancer by more than half (from Cancer Research UK).
And if you really MUST tan, please at least use SPF 15 sunscreen. SPF 5 provides you with virtually no protection at all (do not believe the people on here who say that using SPF 5 provides you with protection. It doesn't). Dermatologists recommend using a tanning lotion with a minimum of factor 15.
Anyway, there's loads of stuff on the internet on the risks. Look at the skin cancer and dermatology websites. They're the most reliable. Don't believe what you read on here, because some of what is being said is untrue.