It depends. It ain't that unusual, but there again, not all of life is down, it has upsides too.
Being in a relationship is nice, but so is the freedom to do what you want. The grass always seems greener on the other side ?
Jobs come and jobs go; when one chapter ends it becomes the start of something new. That may be difficult to see presently, as feeling the loss is easier than acknowledging the opportunities.
Make an effort to meet others, it can lift your mood. See friends at the pub. Join a club on something that interests you. That sort of thing.
Remember that everything in existence is change, so this will pass. Do what you can to find that which is worthwhile in the present moment and appreciate it.
Good luck.