Hello, Thank you for your question You are currently in your third trimester of pregnancy. For women in their third trimester of pregnancy or breast feeding the preferred mode of treatment is hygiene measures (which if followed break the cycle and it is highly likely to get your rid of the infection in 6 weeks time) 1. close-fitting underpants or knickers should be worn before going to bed and changed every morning. This is to prevent you from touching the skin near the anus even if you itch during your sleep. (wearing cotton gloves at night may also be helpful in preventing night-time scratching with fingernails.) 2. Have a bath every morning, or wash around the anus, to get rid of any eggs laid overnight. this routine must be done straight away after getting up from bed. 3. Ideally nightwear should be changed followed by being washed each day. 4. Wash all sleepwear, bed linen, towels, and cuddly toys. 5. Vacuum and damp-dust your home with particular attention to bedrooms, including vacuuming mattresses, and where children play. 6.Thoroughly clean the bathroom by damp-dusting surfaces, washing the cloth frequently in hot water. Do remember to throw out the cloth afterwards. However if these measures do not help or your treating doctor thinks that you are still in need of the medication only then you may be prescribed mebendazole (a category C drug for use in pregnancy which means its use needs to be weighed by your doctor before being prescribed since although not proven/experimented in humans however has shown to have the potential to cause fetal abnormalities in animal studies). So , no it would not be recommended for you to buy any over the counter medication for yourself for clearing out the thread worm infection. Hope this has helped you understand the situation Regards Dr Ali