I've Fallen and Can't Get Up--Need Advice

Ok.  About an hour ago I was home alone after my pool exercises.  Admittedly I did push a little hard in the pool and was feeling particularly tired when I arrived home.  I got out of the bath, parked my scooter and tried to walk (with walker) back to my bedroom (about 40 ft).  Well I didn't make it even with the walker.  I struggled but my legs and lower back were just without strength or were cramping.  Down I went.  My legs couldn't lift and I am not strong enough (yet) to pull myself up.  I did manage to slide to a spot inthe room where I could get better leverage. Even getting to my knees was difficult.  I grabbed on to a rail with both hands and willed myself to my feet.  After resting for an hout or so I am now gingerly walking with a walker...and here I am.

I'm ok. My major issue with this incident are what do you do if you cannot get up.  Are there techniques I should know about getting up and where can I find out.  Maybe someone can shed some light for me.  Should I get some type of emergency Alert system ($$)?   My sister's cell phone was off.  Should I just stay on the floor for a while and try again.  This incident has just made me afraid and if anyone can advise I would appreciate it.

I feel sad.  Like I am not ahle to take care of myself