help!

It might be an issue, but you should try anyways. Sororities don't just judge on your year

You'll be automatically dropped by about half the houses on the first night of rush and it will be pretty hard to get a bid from the others with GPA/ graduating soon after you're initiated. You should still try though! If you're outgoing and have great conversations during rush you may get a bid

If you don't have all the credits to be considered a senior- you can go in as a junior to recruitment.

Phi Sigma Rho is a Science and Engineering sorority, so you might want to check them out. They have a separate recruitment though. In general though your year should not keep you from going through recruitment.

Rushing as a 4th Year isn't the end of the world. In fact, from a statistical standpoint, seniors are one of the best girls to have in a pledge class. In the case that chapters reach quota, seniors don't count towards the quota, so a chapter can take you in addition to all the other girls on their bid list.
However, unless you pick a chapter that does winter or spring recruitment, you won't be able to pick up a little, unless you end up staying for a 5th year.

No it won't be difficult to get a bid! Rush anyways. You won't get dropped for being a 4th year.

DO NOT listen to those other comments! I am currently in a PHC sorority at UCSD and I can tell you for a fact that my chapter would not consider your year or major when considering giving you a bid. The chapters are looking for women to initiate into their respective chapter's lifetime of sisterhood--NOT just for another year. I highly encourage you to go through formal recruitment in the fall, and I don't think you'll regret it. A 4th year who was just initiated into my chapter last year (and graduated last year) said that her only regret was not rushing sooner. I hope you decide to go through formal recruitment in the fall, and the only advice I have to give you is to be yourself. Everyone has a way of finding where they belong in recruitment. :)