The best way to STOP feeling lonely is to "volunteer". Give of yourself and you will feel a lot better about yourself. Everyone has some gift they can share with others. You say you are a teacher, maybe you can tutor some kids after school who can't afford to pay for tutors. Maybe you can volunteer at a nursing home or hospital to work with kids who need to keep up. Maybe you can volunteer to read to others.
Another way to keep from being lonely aside from reading is keeping a journal. Be very tough on yourself and give yourself a time frame or page frame. YOU must write for at least half hour each night, or you must write at least 3 pages every night. Try to get into routines and good habits.
Another thing you can do is take up a musical instrument. When you do that, much of your spare time is taken up with practice and you get a sense of accomplishment as you progress.
If you are taking up reading, you can choose an author and read through his/her entire collection of books, or join a book club whether online or in person at the library. There is something I always wanted to do, and maybe you can do it for your local book store or for the school you work for (library). When I go shopping for my grandkids, the bookstore has no clue what books are appropriate for what age group. I would love to have a written guide according to book or according to author. Who better to do this than someone that has time on their hands and is bored? You can go into your local bookstore or school library and discuss it with them. Then you can call publishers and get their suggestions and start working on it. Who knows you can become famous for the first person that put together such a guide. Also it would be great if you can make a guide/chart for parents to print out for their kids, so they can keep a record of which books they have read so they, their parents and grandparents will know which books to buy and which to steer clear of in their appropriate categories.