I’m trying to draw a state machine for my developed software so as usual in software developing I have several different guards for different transitions which all of them coz to the same state.
Now I want to know is it okay to show all of the loop-transitions and guards ? or do I need to draw only one loop-transition?
Yes, it is. The diagram granularity (amount of details) depends on its goal. If you want to sketch up the big picture of the system then do not show all details, but if you want use the diagram as a complete specification artifact you must draw everything. Redundancy in the state machine can be a sign of poor modeling, so you can use a more complete diagram as a way to improve your modeling minimizing the loop-transitions. There are a lot of programs that can help you on generating state machine diagrams: http://www.gnu.org/software/autogen/autofsm.html and more https://www.google.com/search?q=finite+state+machine+generator