Vaginal discharge is often normal and harmless
You can make sure you do not have an STI by doing a check-up online:
If the discharge is itchy and uncomfortable, you could try a thrush/candida treatment such as fluconazole tablets or clotrimazole pessaries. Clotrimazole cream may also help. You can buy these without a prescription from any pharmacy, or from an online pharmacy. By asking for these generic names it will be cheaper than buying brands (e.g. Canesten).
If the discharge has an unpleasant smell, you can try lactic acid gels, such as Balance Activ or Relactagel (or an 'own-brand' equivalent). You can get these from pharmacies or online, including from Amazon.