What Causes Longer Erection With Condom Compared To Without Condom?

Good day Dr. Kumaresh Krishnamoorthy,
I want to start by telling you series of problem i have encounter in details..i believe using condom is stopping one girl friend to get unwanted pregnancy ..And other related disease but. When i used condom in making love to my girl friend i stay longer more than without condom for instant. I could make love with condom on for almost 45minute or more but without condom i can't stay more than 10minute why is that?

And sometimes i could make love for hours when i get in the mood of doing it but that with condom ...well maybe you could help me with explanation of details

2: My sperm count also low at the moment. years ago i could easy get woman pregnant 2time a month that when i don't used condom and also just want to know what tablet i could buy to help me increase that low sperm to become better and because i am scare if this continue would be problem in near future i am just 29years old