I Am A 35 Year Male , Loving A Girl

i am a 35 year male , loving a girl of 28 years old ,, from 5 years back we were in sexual relations , it was very good , 3 years back i was diagnosed with diabetes and in these 3 years we tried sex 8 month back, but it was difficult to penetrate because penis was not hard. i tried many times but not possible , in these 8 monyhs i controlled my diabetes , now it is normal without any tablet .
i found on net that because of diabetes it affected my sex organ and its erectile dysfunction.
i am going to marry that girl in next 6 months, but i want to give her that pleasure which i gave her 5 years back.please suggest me tablets , i dont want to goto any doctor because of shyness