Thanks for your query.Based on the facts that you have posted it appears that you have problem of voiding symptoms along with erectile dysfunction
If your symptoms are severe and if there is significant residual Urine it will be better to undergo surgery for resection of prostate
( TURP) or may opt for medical line of treatment with Tomsuloine combined with Phospho Diesterase Inhibitors like Sildenafil
Please consult qualified Urologist
for clinical assessment and advice as regards further treatment.