I suspect your paper development time is too short. Paper is usually developed to completion, so additional development time shouldn't affect the image much. I would suggest you try a much longer development time - say 5 minutes. If your image goes too dark, then reduce the exposure but do not change the development time. Once you've found the correct exposure, you can start reducing the development time.
I would also suggest you try contact printing, to eliminate the possibility that it is a light leak from the developer. If your contacts come out well, but your enlargements don't, then that's probably the problem. When you contact print, leave the enlarger head at the same height as for an enlargement; that way, you should get the same exposure on the contact print as on the enlargement.
I would also try a fresh stock of "known good" paper. For me, "known good" would be Ilford. Although Ilford Multigrade IV is what I use, it might be worth getting a few sheets of graded paper (Ilfospeed RC deluxe) in Grade 3 (since that is what you used to print with). That way, you will eliminate the possibility that your projector bulb or contrast filters are faulty.
And like everyone else says, test your safelight. Or at least develop a print in the dark!
Essentially, if you contact print onto fresh Grade 3 graded paper and develop for plenty of time in the dark using fresh developer, then you will have eliminated all the likely causes of poor contrast (assuming your negs are good, of course). Once you've got a print that shows good contrast (even if it's not the final print you want) then you can start adding the variables back - develop for a shorter time; turn the safelight on; use multigrade paper with the appropriate filter; print an enlargement instead of a contact print. (Don't make all these changes together; make them one at a time). This should show you where the process problem lies - bad safelight, bad filters, enlarger bulb, development time, etc.
Good luck and please let us know how it works out!
Andrew