Hello
Normal erection does bend upwards n in some towards abdomen... If u r able to penetrate and ur partner is not having pain, that means the shape of ur erect penis is normal!
Ur masturbation technique is unlikely to affect ur curvature..
Regarding premature erection--
According to large studies- adequate duration of intercourse is just 4-7 minutes! I am sure ur duration is also same.
If not, or if u want to prolong it anyway
1. Try wearing a regular condom during sex- this will decrease sensations on penis and prolong lovemaking
2. Or pull out ur penis just before u r about to have orgasm ... N apply pressure on the tip of penis..this will make ur urge to ejaculate go away. Once it does, continue the sex.
3. Try long last condoms ... Wear them as soon as u r erect and are doing foreplay.. these condoms have benzocaine , which decreases sensation on tip of penis.. temporarily, and help prolong sex.
Health Tips
Don't go by what they show in adult films... it is not authentic