As most of us know, the earliest sign is a missed period but this could also be down to stress or other factors. The easiest and quickest way to answer your question is to take a home pregnancy test, which can be taken from the first day of your missed period. They're usually pretty reliable but if you're unsure, contact your GP and get booked in.
In most cases it's totally safe to have sex when pregnant, though you may want to avoid putting too much pressure on your bump and breasts! If you have a high-risk pregnancy or have had any bleeding then it's worth consulting your midwife or doctor first, just to be on the safe side.
Unfortunately the answer is yes. As the bleeding is mostly the lining of the womb it's totally normal to have vaginal bleeding after a caesarean, just as you would for a vaginal birth.
We would advise against this straight after birth as your vagina needs time to heal and using internal protection could increase the risk of infection. You're best to wait for your 6 week check, where your midwife will inform you if you're okay to use tampons.