How to prevent bleeding during pregnancy?

After the bleeding on my 13th week gestation, I had 3 times light spotting of bleeding. This Tuesday it happened again! The bleeding is always painless, sometimes bright red. And to me, it always happened during the early morning.
What causes placenta previa? Is there any treament besides just wait and see? How to prevent the bleeding? With all these questions in mind, I went to online today to search for information.
According to the information online, The exact cause of placenta previa is unknown. It may be caused by multiple pregnancy, an abnormally shaped uterus, older age of the mother, a previous cesarean birth or induced abortion. Bed rest, avoiding intercourse, limit traveling and avoiding pelvic exams are the treatment suggested by online resources. Overall, it seems there is not too much I can do besides being careful with myself and taking more rest.
However, to my surprise, there are a lot of worried mothers-to-be seeking for concrete advice on how to prevent or limit bleeding related to placenta previa.
Recalling the last 2 months, I summarized the following tips from my personal experience:
1. Be careful with contipation. The push of the bowel musles can easily cause the bleeding. Eat more vegetables, fruits and drink more water to prevent contipation.
2. No heavy lifting. Don’t lift staff heavier than 5 pounds. Seek for others’ help when you need to move something.
3. Bend at the knees to pick up something. Don’t lift abruptly. Bend at the knees slowly and stand up slowly too.
4. Lie down/get up slowly. Don’t jump onto/out of the bed. A good way is before going to bed, go to the edge of the bed, lie down slowly with your side and then turn onto your back. Similarly, when you want to get out of the bed, turn to your side and get up slowly.
5. Don’t wear high-heeled shoes. Wear soft and flat bottom shoes.
6. Always hold on something when you climb stairs, especially downwards.
7. Be careful with doing exercise. Avoid those fast-paced exercises.
8. The last but not the least is, being relaxed and happy. You don’t need to always keep it in mind!