Issues With Premature Ejaculation And Erection. On Tribulus Terrestris Ext. Suggestions For Remedy

I am taking Tribulus Terrestris Ext. Compound regularly And if I take “Viagra” (Sildenafil Citrate) 50 mg once a week (before "Sexual Activity",) and don’t take Tribulus Terrestris Ext. Compound on that day, will it be safe.
Currently I am not taking any kind of medicine for this purpose, but I am having problem with "Premature Ejaculations" and little problem erection.

I had done Coronary Calcium Score Scan in January 2012 which showed calcium Score "0", which means chances of coronary Artery Disease is less then 5%. .

I have gone through Laparoscopic Bilateral Hernia Repair on February 20, 2013. Now ok

I have a history of hypertension (Dystolic) for the last 10 years and my blood pressure remains normal with medicine. currently I am taking:

Lisinopril Dihydrate (ZESTRIL) 20 mg - morning
Bisoprolol Hemifrmarate (CONCORE) 5 mg - morning
Amlodipine Besylate (NORVASC) 5 mg - night
Additionaly I am taking Allopurinol (ZYLORIC) 100mg - night

I would appreciate if you could guide me accordingly.



AKBER SULTAN