Using condoms correctly and consistently greatly reduces the risk of contracting sexually transmitted diseases/ STDs. But still condoms might not offer absolute protection due to factors like skin-to-skin transmission and condom breakage.

In that case you need to consult a sexual health specialist. Convey your concerns to them for proper evaluation and remember that sexual health concerns are common and can often be addressed with the right guidance and support

Burning after urination is a sign of urinary tract infection.. Drink plenty of water and consult a doctor.. Antibiotics can cure UTI. Don't delay, UTI can worsen. 

Essentially, a varicocele occurs when the veins within the scrotum expand, causing them to fill with blood – but commonly without any symptoms. Some people might experience a kind of achy pain or heaviness. It is not harmful at all to masturbate when you have it. If the valves in the veins aren’t working properly this could lead to what causes them in most cases. 

Treating premature ejaculation can include medications, psychological counseling, and sexual therapy. Psychological counseling and behavior therapy can help address underlying psychological issues that may be causing or contributing to the problem. Sexual therapy can help couples address relationship issues that may be contributing to the problem.
PS- Medications and treatments can be prescribed only after a proper diagnosis.