Paradoxically, taking too many stool softeners and laxatives can actually be a common cause of constipation. Metamucil is good to take every day, but you may want to stop taking the other stuff and give your body time to adjust. Are you drinking a lot of water? That can help relieve constipation, along with eating fruits and vegetables (do an internet search for ones that are highest in fiber). Exercise can also keep you regular.

Are you taking any medication? Some medications can cause constipation, so you may want to look at the side-effects to see if anything you take does. You also mentioned drinking a lot of soda, you may be getting too much caffeine, which can cause dehydration.

Going only once a week is probably too infrequent, but not everyone goes every day. Some do three times a day, some three times a week. It depends on what's normal for you.

Try changing your diet and see if things don't get better in a couple of weeks. If they don't, go see your doctor. It could be IBS, but there are a lot of other disorders that need to be ruled out first, such as hypothyroidism, diabetes, as well as digestive disorders. Make sure they do tests for other things before they just dismiss it as IBS, as a lot of doctors seem to do.