Accepting that this information is correct: “It has worked before on my iPhone”… Maybe if you approach the issue in a linear fashion it will help reveal some information that is actually useful.
Symptom:
Doesn’t work on your iPhone anymore, and it stopped around 3rd week in march.
Reasonable theories:
1) Something on your site has been changed, and is now preventing viewing on your iPhone.
2) You’ve changed something on your iPhone that’s now causing issues with viewing your site.
3) Both 1 and 2 might apply.
Start testing your theories:
The very first, and glaringly obvious step to take, is to see if your site is viewable on someone else’s iPhone. Preferably a consensus of “three” separate tests with three separate iPhones would immediately answer the question: “Which do I need to address, my web site, or my iPhone”? Secondary to that, you might check and see if anyone can view it on an iPad or an Android, or any other non-iOS handheld device with a browser. Could reveal some good information to get you pointed in the right direction.