You need to go for a full examination with a dentist that you feel at ease with. At this stage they will give you a full treatment plan for the treatment needed to give you a healthy mouth and get rid of your pain.

Once this treatment has been completed, you will then be in a pain free situation and can think abut what can be done to improve the appearance of your teeth. A denture cn be made for you to fill in the missing teeth. If you improve your oral hygiene by brushing a flossing twice a day and seeing a hygeineist regularly, then bridges may be a solution for you gaps. These a fixed restoration unlike a denture. I think  that at your age this would be a nice option for you but if you do not improve your oral hygiene first of all the dentist will not place them for you and second of all, if they do, they will fail causing you further problems.

You need to cut back on your sugary drinks.

You should be able to get most of the above treatment on the NHS and privately, so would just be whichever you opt for.

Kind regards

Dr Glaister