There is no chance of getting pregnant from sperm touching your skin.

You could have a yeast infection, they can make your vagina itch and burn. You did well starting to use Candid B cream and taking lactobacillus capsules, but I'm afraid things have only gotten worse since your period started. Keep taking the traco exactly as directed along with the lactobacillus capsules. Make sure that you continue keeping the affected area clean and dry while avoiding scented products too. If these measures fail to relieve your symptoms please make an appointment with your doctor for further advice.

You can get pregnant during periods. It needs to be highlighted that it is possible for pre-cum to bear sperm so that is why the possibility is very low.  If you are pregnant, you may see symptoms such as nausea, and painful breasts. It could be down to missing your period and simple diseases like nausea and breast tenderness can be the first sign.

Masturbation is a normal and healthy behavior . . No need to worry 

Vaginal itching can be caused by several factors: infections, irritants, and allergies. Yeast infections, bacterial imbalances, or sensitivity to soaps and laundry detergents are the common causes. To manage the problem, it is important to practice good hygiene, use breathable fabric, and stay away from harsh products that could worsen the symptoms. Nonetheless, it is necessary to visit a physician and undergo specific diagnosis and treatment. They would be able to study your case and advise proper healing methods. Keep in mind, getting help is the right way to make yourself feel better and to secure your health.