Pubic lice (also known as crabs or scabies) are tiny insects that are found on coarse body hair, such as pubic hair, underarm hair and occasionally in beards. They don't live in the hair on your head.
They can be passed on through close bodily contact, for example through sex. Using a condom cannot prevent you from getting pubic lice. The best thing to do is just to visit a healthcare worker if you think you have the symptoms. The main symptom is itching in the affected area - especially at night. You might also notice some inflammation caused by scratching, black powder in your underwear and blue spots or small spots of blood on your skin.
To know if you have pubic lice a healthcare worker will examine you. Once diagnosed you can treat the pubic lice by using an insecticide cream, lotion or shampoo.  

Thrush is an infection caused by a yeast fungus. It can affect your vagina, penis, mouth and in rarer cases other areas of the body. It's not considered a sexually transmitted infection, but it can be brought on by sex and sometimes passed on through sex, although this isn't how most people develop thrush.
Thrush is very common and usually harmless. It's estimated that 3 out 4 women will have thrush at some point in their life. Men can also get thrush, but it's less common. Often people won't notice any symptoms, but it can cause a thick white discharge from your penis or vagina as well as itching and irritation around the genitals. As these are common symptoms for other STIs too, it's important to see a healthcare provider if you notice these symptoms.
You're more likely to get thrush if you:
 1. wear tight clothing
 2. use soaps or other products on your vagina
 3. have diabetes, HIV or other Illnesses that affect your immune system.
Thrush is easily treated with anti-fungal medication.

Urinary Tract Infections (UTI) are infections that occur in the urethra, the tube that your pee comes out of. They're much more common in women than men because women have a shorter urethra. They're not sexually transmitted and not contagious. However, women can often get UTIs after sex, this is because bacteria can be introduced to the urethra during sex.
To avoid getting UTIs, it's a good idea to pee before and after sex. You should also avoid doing things that might transfer bacteria from the anus to the vagina and urethra, for example moving from anal to vaginal sex. If you do this, you should use a new condom for vaginal sex. It's also a good idea to wash your hands before touching your partner's genitals.
In mild cases, UTIs will get better by themselves. Try to drink lots of water and don't hold in your pee. If the infection lasts longer than 4 days, you should speak to a healthcare worker. It's also a good idea to speak to a healthcare worker if you've not had a UTI before, as sometimes the symptoms can be similar to STIs. They can also prescribe you antibiotics to treat the infection if needed.