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Itching in vagina could be suggestive of vaginal infections. This can change the vaginal secretions making them hostile for sperms to survive. If infection spreads upwards, it can change cervical mucus making in impossible for sperms to pass through it. Consider visiting your doctor/gynecologist for further evaluation and assistance. Get started on appropriate treatment. If infective cause is detected, get your partner also treated simultaneously to prevent chances of re-infection. Drink plenty of water. Take adequate rest. Avoid vaginal douching, use of harsh soap or perfumes in the area. Use loose cotton undergarments and avoid tight fitting clothes.
If you are not being successful with your pregnancy plans, consider going ahead with getting infertility work-up done for you and your partner to see if there are any underlying causes for the infertility/inability to conceive. Treatment as needed (based on examination and investigations results) would be started to help you get pregnant. Consider visiting your gynecologist/obstetrician for further evaluation and assistance and be in regular follow-up.
Take care.