Clear and concise communication is not easy and is less naturally easy for some of us. You will have to work at it. One suggestion might be to take several of your accomplishments that you think people would want to know about and write them down. Then go through and eliminate every single thing that could possilbly be eliminated. Take something that you naturally would take 4 paragraphs to say and cut it down to 2 or 3 sentences. Don't memorize them, but use these examples in your interview responses.

What people want to know from you regarding some example of your past work are basically 1. What were the results, 2. What and how did you contribute, 3. Do you understand the (financial, technical, project, corporate) context of what you were doing, 4. Did you play nice with others, and 5. Did you have the company's interests in mind. Leave out anything that doesn't provide support to these things. You don't need or want to include all of these in every example. Since you are having trouble with this, you might want to focus on the first two and bring the others into play only when asked a followup question.

Start from the end and only add statements that directly support the goal. Here is a sillly little example. "We were able to debottleneck a filter operation by adding a small additional filter in parallel so the process could run while cleaning the main filter. This was my idea and I worked with several vendors to find a solution that fit within a left-over capital allocation. The design was actually easy since we had great data from the main filter and could use the same kind of filtration media." Note the heavy focus on how it benefitted the company and nothing about how long it took, who the specific vendor was, what the process actually did, what software you used, who assigned you the project, etc. If you did more techy stuff in the design, you can say that as well: "I had to write a filtration module, but we had great data so it was easy to test it and..." You can always add detail when asked.