Do I need to pay estimated taxes quarterly if I make enough trading stocks?

I have a full time job and have started trading stocks few months back. Already I have enough realized gains that will force me to pay additional tax. My question is do I need to pay estimated taxes quarterly based on the profits I have made so far or can I wait till the end of the year to pay my taxes.
Any one who has been in this situation, if you can share your experience, it will be greatly appreciated.

whats the last trading amount in trading stocks?

I have a doubt that when we order to buy shares without limit price itll get executed with the last traded price means every sec the price oscillate then how cum we can be sure that the shares are bought at the price that we looked for?Then please some one tell me about mutual funds basically i dont have any idea about it,
Id be thankful to you if u resolve these questions