In short, no- I don't know how to "make" someone ticklish.
Here are a few ideas to explore, in case the issue isn't your lack of ticklishness but rather lack of exploration- I have had several ticklees who claimed they were not ticklish and never had been, who were then a mix of surprised/delighted/panicked to discover that they were indeed ticklish and that no one had done so properly.
1) Have your boyfriend try different kinds of touches- soft, hard, slow strokes, fast scribbling... see if that has any effect.
2) Try different implements. I had one 'lee who had almost no reaction to fingers on the soles of her feet, but a feather dragged between her toes made her desperately hysterical.
3) Try letting him tie your ankles together. I have seen this go both ways, but sometimes the inability to move surfaces a sensitivity that you wouldn't suspect.