@Flo *************
if your last stamp is only 7 days old and you haven't left Thailand yet, then get a re-entry permit before you do leave (you can get it at the airport).
It will allow you to use the reminder of your 60-day stamp, which you should then be able to extend at immigration for another 30 days.
Re-entry permits are available in single and multiple variants. Since you will still be using your February entry stamp, immigration will hopefully not have an issue.
If you do get back in, look into one of the other visa options that are available for your kind of travel, as others have advised. You could also look into them while you are outside Thailand but some can only be applied for in your home country or a country in which you are a resident.
You have had two warnings so you should assume that your card is marked and that you will face additional scrutiny when entering visa exempt (and maybe even with a visa depending on which one you get).
Another option would be to fly to a neighbouring country and enter by land, assuming you haven't done so already. Last time I checked you could enter by land, visa exempt, twice in a calendar year (search the forums because I'm not up on recent conditions at the various land borders).
Finally, you can pay a company to bring you in without immigration problems. This applies both to air travel and land border crossings.