Been on Omeprazole for 5 days, no side effects to start with and ...

Been on Omeprazole for 5 days, no side effects to start with and it does seem to have reduced the burning in my stomach slightly, but just today I feel like I've done a heavy aerobics class, all my muscles ache, which makes me feel even more tired and out of sorts than before. I am on Omeprazole to treat gastritis which might be what is causing iron deficiency anemia and B12 deficiency I have been diagnosed with. Many of the symptoms listed in other articles I had before I started Omeprazole - perhaps because of deficiencies. e.g. confusion and not being able to concentrate, utter tiredness, dizziness, massive leg cramps, blurred vision, occasional feeling of heavy heart beat, bloating, having to sleep sitting up, waking up far too early and not being able to sleep again, depression for no reason.