Can I fix my opal triton electric shower?

Have had for 10yrs now. Used to leave it at 2 red line,dial number 6 for 8years. Last year it started getting too hot at that setting and had to put it down to 1 red line at dial 6.Now even that is scalding. If we turn it to 5 at 1 red line.....low pressure kicks in and it alternates between red hot and freezing cold. Is it time to renew?