Just for the record, the raising your arms/umbilical cord around the neck is a complete old wives tale and there is no truth in it.
Listen to your body is the answer with the original question, if you are comfortable and it doesn't cause you any pain/discomfort you can do it unless there are particular medical conditions or situations that say differently (which doesn't sound like the situation for the OP).
And just on the bleeding/rest thing, as someone who has had 4 miscarriages (early) it has been proven that whether or not you rest or keep doing normal activities makes no difference to whether or not you will miscarry; again different if it is later in the pregnancy or there are other medical conditions. it certainly won't do any harm though if that's what you feel like doing. Really hope it is all OK