How did you come up with a loose vagina being the cause of your problem with mediocre sex? When didit become an issue, after childbirth or not? Were you told that's the problem or was it you that first noticed the sex wasn't the way it used to be if that's the case or has it always been an issue? I'm concerned that a lazy or inconsiderate lover may be trying to convince you that the problem is you when that may not be true at all.
Before considering surgery, try other less drastic options. There are products that will help such as these:
Products Designed for Kegel Exercises - Kegel Exercise Products
Are you just doing the kegels on your own or are you doing them with him inside? Whether you do those, the actual intercourse is really just a part of a fulfilling sex life. If the right type & amt of foreplay is done, the sex would still be great even if the penetration doesn't feel quite the same.
So what else is going on that is making the sex not so great anymore?