I ve been on 225mg venlafaxine for a few years prescribed for general anxiety and depression I still feel very low depressed a lot of the time what wo?

Its time to change. It's not uncommon for medications to loose efficacy after a while. There are ways of dealing with it, either switch to another medication or augment the existing medication with another. It important to not forget importance of therapy. Cognitive behavior therapy has been proven to help in anxiety and mood disorders. Please consult your psychiatrist.
Another med, therapy. You should talk it over with your prescriber. No antidepressant works for everyone, and there are many to choose from. Also, anxiety and depression sometimes respond better to psychotherapy than to meds. If you are not in therapy already, please consider adding it to your medication treatment. And make sure you have good nutrition and moderate exercise to help yourself, too.