The only way in which you will get such an infection is if the pillow is dirty!! But what you actually need to do is to focus on why you still resort to pillow talk for this gratification. Look at seeking some companionship. If you feel that your excess weight is creating problems for your self esteem, look at ways of reducing weight as soon as possible. It might help for you to consult a counsellor to help you resolve some of these issues.