It is not wise to start exercising in pregnancy, but it is perfectly fine to continue your exercise regimen unless advised by a doctor to stop.

So the 2-3 weeks when you may not know you are pregnant is what you are asking about? No. There shouldn't be any problem. Most early miscarriages are caused not by what a woman has done but by chromosomal abnormalities. Nothing can be done to prevent early miscarriage.

The reason I ask is because I already do exercise, but I work out pretty hard. When I'm pregnant I'll be high risk and will have to be extra careful about everything I do though the Dr hasn't told me to stop exercising altogether.
I felt some weird pains in my lower abdomen after exercising a week and a half ago, and I think I may have been pregnant as my period came and the blood has globs in it.

How do you know that you will be high risk when you get pregnant?

If your period came at the normal time, then it wasn't a 'miscarriage'. Those globs are blood clots that are caused by the lining of your uterus shedding. There is nothing mysterious about them.

What is your pregnancy risk factor? Do you have an incompetent cervix? Have you had multiple early stage miscarriages? If you are concerned about your exercise intensity and think you may be pregnancy, scale it back a smidge. Or you could always ask your own personal doctor who knows your history and your risk factors. S/he could tell you far better than anonymous strangers on the internet giving out general advise.

For the most part, to answer your original question, no, exercise does not pose a risk for a blastocyst that is under weeks. In fact, a lot of women do a lot of things not ever knowing they are pregnant. And lets not foget, women have been working hard in the fields with men right up until delivering their baby - then they strap that baby to their back with a blanket and head back out.

I know I'm high risk because the Dr. told me I am. I had a miscarriage and 2 uterine surgeries in the last year and a half. Because of that I am high risk.
Just so you know, I am not stupid, I was asking a simple question. My periods usually don't have globs of blood in them and I have never gotten the tearing/pulling pain in my uterus before my period until now. My period was a couple of days late too. My Dr. is a reproductive endocrinology specialist (who I was referred to because of the severity of my situation) and costs over $200 a visit for just 10 min. of his time. For a little question that slightly concerned me I thought I'd get some input, but obviously this was the wrong course of action to take.

I don't understand why you're upset. Nobody here has talked down to you. They've answered your questions without patronization or rudeness.

I'm sorry to have confused you, but I feel very patronized and talked down to. That's the main reason why I'm leaving this site. Good Luck to everyone here and hopefully you'll learn to be less judgmental and abrupt.