If I have bad teeth n gum issues n cavities will a waterpik cause me pain there's a few teeth I can't brush dentist recommend waterpik worried pain?

Dental Care. Have your teeth professionally cleaned first, then have all your carious teeth restored. Then use the waterpik to maintain your newfound good oral health.
Careful,Good Luck. A waterpik can be a good thing when used properly. First , however you must have a complete cleaning so that you do not risk blasting the bacteria deeper into the tissues. Use warm water and start on lowest setting. Best to bring to Dental appointment and have hygienist / Dentist show you how to use it safely. Follow-up on your good start and get those treated - one thing at a time if necessary.
Modern Dentistry. A Waterpik can be a good thing when used properly. First , however you must have a complete cleaning, gum treatment and tooth sensitivity and decay under control. Fortunately, modern dentistry has lots of tools to keep your teeth in shape.