A few thoughts .....
1) While you are busy fundraising for your cause, half your coworkers/friends/family/acquaintences, etc. are also doing the same thing for their causes.
One particular year at a place I used to work, this became a real problem!! Every week, sometimes several times a week, another coworker came through the office with some sort of fundraising thing .... cancer, diabetes, their kid's band or sports team, etc. etc. etc. The going rate for each of these was a $5-10 donation. I was one of the lowest paid employees in that office, and it didn't take long for me to realize I was shelling out a heap of money for all the things which employees, making twice what I was making, were pushing. I quit donating.
Something must have been said, because after that year there was only one form of fundraising ... selling chocolates. The seller would set a box of chocolates on the front desk with a note indicating their price and what the money from the sale of the chocolates were going for. No pressure ... but at least we felt like we were getting something for our money ... a yummy chocolate bar!
2) These days I do not give money to any organization unless the person who is fundraising is willing to give me the website, brochures, and all the paperwork to tell me what it is for, where the money is going, etc. It's interesting ... I've had phone calls where someone has wanted me to send money to some cause or another, but when I've asked for paperwork and additional information, they've refused to send me any information ... they just wanted me to tell them my credit card number or send a cheque. Nope. Sorry.
3) I did the MS150 ride one year and did fundraising for that. I raised a little bit more than the minimum, but fundraising is not my thing ... I feel like I'm begging. So, unfortunately, I've never done a MS150 ride since. And I've heard they raised the minimum fundraising limit. If they had lowered it to about half what it was, I might ride more of them because I could either just pay the minimum myself, or do a limited fundraising endeavor. And I know there are quite a number of other people who feel the same way.
4) Time limits - it's one thing if you make a fundraising run through the office for an event that is going to take place within a few weeks or month. People feel like there will be an end to the constant mental pressure and guilt that they should be giving, or giving more. (Not saying you are imposing mental pressure and guilt - but people just feel pressured and guilty when they know that someone with a fundraising project is present). But you've mentioned that you have only been doing this since Feb ... that's 4 months!! That's a long time!! When is the event you are raising the money for?