Well, you know my advice re PREVENTING constipation .... that still stands but is of little help if you're already bunged up!
First you need to clear 'the backlog' and I found Dulcolax perles were good for that. Read the label carefully because I didn't and took four (well, they ARE tiny!) OMG - I almost turned inside out!!!
There's a new product out that I saw on TV yesterday and it helps soften stools to make them easier to pass ... Think it's called 'Dulco-ease'. Might be worth checking out.
Once you're comfortable again then do all you can to get some bulking agents inside (e.g psyllium husks) on a regular basis to prevent the same thing happening again.
Good luck!!