Diazepam 15 years, now sertraline, both together ' and it's increasing anxiety and making me short of breath?

Drug interaction? Shortness of breath has been a reported drug interaction between sertraline and propanolol which you're also taking. Review with prescribing doctor with out delay. Hope this helps.
Surprising. This is hard to understand and it suggests that something else is going on. You would be wise to get a full evaluation.