Regret??

Please no harsh comments and please don't think i'm taking my baby for granted.
When i first found out i was pregnant, i had just started to get into shape, i was going to get a job and study and all of thats been put on hold!
My son is 5 months old and i love him to the ends of the earth, but me and the dad have split up, i've put all my weight back on and i'm trying to start studying, im on centrelink and i just feel like im a failure!
I feel like if i had the chance, i wouldnt of had my baby because i dont feel strong enough to raise him on my own...
im constantly in tears, im sad because his dad left me and doesnt want me back and then im sad because i have bigger problems than romantic.
i dont know! :(